Long-Term Debt (Details Textual)

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Long-Term Debt (Details Textual) (USD $)	12 Months Ended				12 Months Ended				12 Months Ended							12 Months Ended				12 Months Ended								9 Months Ended	12 Months Ended		12 Months Ended														12 Months Ended			12 Months Ended					12 Months Ended				12 Months Ended			12 Months Ended
	Dec. 31, 2012 Agreement	Dec. 31, 2011	Dec. 31, 2010	Sep. 23, 2009	Dec. 31, 2012 Assumed Notes [Member] Notes	Dec. 31, 2012 9.0% Senior Subordinate Note due 2018 [Member]	Dec. 31, 2011 9.0% Senior Subordinate Note due 2018 [Member]	Mar. 12, 2010 9.0% Senior Subordinate Note due 2018 [Member]	Dec. 31, 2012 5.0% Convertible Senior Note due 2029 [Member]	Dec. 31, 2011 5.0% Convertible Senior Note due 2029 [Member]	Dec. 31, 2010 5.0% Convertible Senior Note due 2029 [Member]	Jul. 27, 2012 5.0% Convertible Senior Note due 2029 [Member]	Jun. 30, 2012 5.0% Convertible Senior Note due 2029 [Member]	Sep. 23, 2009 5.0% Convertible Senior Note due 2029 [Member]	Dec. 31, 2012 7.0% Senior Subordinated Notes due 2022 [Member]	Dec. 31, 2012 5.0 % Convertible Notes [Member]	Dec. 31, 2011 5.0 % Convertible Notes [Member]	Dec. 31, 2012 Other Debt [Member]	Dec. 31, 2011 Other Debt [Member]	Dec. 31, 2012 Senior Subordinated Notes [Member]	Jul. 02, 2012 Senior Subordinated Notes [Member]	Dec. 31, 2012 Mortgage Loan at Fix Interest Rate [Member]	Dec. 31, 2011 Mortgage Loan at Fix Interest Rate [Member]	Dec. 31, 2012 Mortgage Loan at Variable Interest Rate [Member]	Dec. 31, 2011 Mortgage Loan at Variable Interest Rate [Member]	Dec. 31, 2012 Mortgage Notes Payable [Member]	Dec. 31, 2011 Mortgage Notes Payable [Member]	Sep. 30, 2012 Mortgage Notes [Member] Properties	Dec. 31, 2012 Mortgage Notes [Member]	Dec. 31, 2012 2011 Used Vehicle Floor Plan Facility [Member]	Dec. 31, 2012 Derivative Instruments and Hedging Activities [Member]	Dec. 31, 2011 Derivative Instruments and Hedging Activities [Member]	Dec. 31, 2010 Derivative Instruments and Hedging Activities [Member]	Dec. 31, 2012 Derivative Instruments and Hedging Activities [Member] Other Accrued Liabilities [Member]	Dec. 31, 2011 Derivative Instruments and Hedging Activities [Member] Other Accrued Liabilities [Member]	Dec. 31, 2012 Derivative Instruments and Hedging Activities [Member] Other Long term Liabilities [Member]	Dec. 31, 2011 Derivative Instruments and Hedging Activities [Member] Other Long term Liabilities [Member]	Dec. 31, 2012 Maximum [Member]	Dec. 31, 2012 Maximum [Member] Mortgage Loan at Fix Interest Rate [Member]	Dec. 31, 2012 Maximum [Member] Mortgage Loan at Variable Interest Rate [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Minimum [Member] Mortgage Loan at Fix Interest Rate [Member]	Dec. 31, 2012 Minimum [Member] Mortgage Loan at Variable Interest Rate [Member]	Dec. 31, 2012 Weighted Average [Member]	Dec. 31, 2012 2011 Revolving Credit Facility [Member] Rate	Dec. 31, 2011 2011 Revolving Credit Facility [Member] Rate	Dec. 31, 2012 2011 Revolving Credit Facility [Member] Maximum [Member]	Dec. 31, 2012 2011 Credit Facility [Member]	Sep. 30, 2012 2011 Credit Facility [Member] Maximum [Member]	Dec. 31, 2012 2011 Credit Facility [Member] Maximum [Member] Required ratio [Member]	Sep. 30, 2012 2011 Credit Facility [Member] Minimum [Member]	Dec. 31, 2012 2011 Credit Facility [Member] Minimum [Member] Required ratio [Member]	Dec. 31, 2012 2011 New Vehicle Floor Plan Facility [Member]	Dec. 31, 2012 2011 New Vehicle Floor Plan Facility [Member] 2011 Used Vehicle Floor Plan Facility [Member]	Dec. 31, 2012 Paid-In Capital [Member]	Dec. 31, 2011 Paid-In Capital [Member]	Dec. 31, 2012 Paid-In Capital [Member] 5.0 % Convertible Notes [Member]	Dec. 31, 2012 Common Class A [Member]	Dec. 31, 2011 Common Class A [Member]	Dec. 31, 2012 Common Class A [Member] 5.0% Convertible Senior Note due 2029 [Member]	Jul. 27, 2012 Common Class A [Member] 5.0 % Convertible Notes [Member]	Jul. 02, 2012 Common Class A [Member] 5.0 % Convertible Notes [Member]
Long-Term Debt (Textual) [Abstract]
Stock issued																																																									4,100,000
Stock issued																																																										4,075,000
Notes maturity date						Mar. 15, 2018			Oct. 01, 2029											Jul. 15, 2022
Stock price per share	$ 16.6554								$ 16.6554
Interest on notes	5.00%	5.00%			5.35%	9.00%			5.00%						7.00%	5.00%				7.00%																		10.52%	7.03%		9.52%	4.07%		10.19%											5.00%	5.00%
Receive Rate	one-month LIBOR
Debt weighted average interest rate on note																													4.62%
Interest rate																																													2.25%	2.25%
Common stock, shares issued																																																										61,352,134	56,377,778		4,100,000	4,100,000
Discount associated with notes						$ 1,100,000	$ 1,200,000			$ 17,700,000					$ 1,700,000		$ 17,700,000									$ 700,000	$ 900,000
Premium associated with notes	700,000	1,200,000			700,000
Maturity date of 2011 Revolving credit facility and Floor plan facility																																																Aug. 15, 2016
Increased Borrowing Capacity																																													225,000,000		175,000,000
Percentage of fair market value of common stock to calculate available credit facility																																													50.00%
Number of common stock shares pledged as collateral																																													5,000,000
Increase in Credit facility Borrowing Capacity																																																						175,000,000
Borrowing Base																																													175,000,000
Letters of credit outstanding amount																																													34,800,000
5.0% Convertible Notes	629,385,000	547,619,000			10,600,000	210,000,000	210,000,000			155,055,000					200,000,000			5,431,000	5,752,000			137,791,000	116,584,000	62,229,000	65,640,000																				6,176,000
Borrowing available																																													134,000,000
Minimum Outstanding Balance for Maturity date Extension																																													35,000,000
Maximum Borrowing Capacity under 2011 Used Vehicle Facility																														80,000,000																							500,000,000
Allocation of Credit Facility Increase, percentage																																																					15.00%
Debt Conversion, number of shares for weighted average pricing																																																												30.2070
Total amount paid in cash on conversion of debt									137,100,000
Debt extinguishment charges									20,900,000
Amount charged to interest, expense and other	60,090,000	66,857,000	73,179,000						1,200,000
Final consideration for convertible notes	1,503.11
EBTDAR to rent ratio																																																	3.00	1.50	1.00	1.00
Unsecured senior subordinated obligations, description						9.0% Notes
Debt instrument date of required interest payments						semi-annually on March 15 and September 15 each year
Debt instrument earliest redemption date						after March 15, 2014
Indenture 9.0% notes						101.00%
Restrictive covenants						Dec. 31, 2012
Interest expense associated with amortization of debt discount and deferred loan costs									3,500,000	6,700,000	6,400,000
Interest expense related to Convertible Notes									4,200,000	8,400,000	8,700,000
Mortgage financing aggregate																													200,000,000
Mortgage financing related to dealership properties																												21
Fair value of swap positions																															34,300,000	37,600,000		12,100,000	13,200,000	22,200,000	24,400,000
Notional forward	2
Interest rate cash flow swap agreements	100,000,000
Duration of Interest rate cash flow swap agreements	July 2015 and terminate in June 2017
Incremental interest expense	13,400,000	17,700,000	17,600,000
One-month LIBOR rate	0.209%																																							3.50%			1.25%
Net expense expected to be reclassified	7,500,000
Aggregate principal amount								210,000,000				1,000		172,500,000							200,000,000
Notes issued at a price of principal amount																				99.11%
Notes issued yield maturity, percentage				5.00%																	7.125%
Debt discount on notes	2,780,000	5,158,000	5,195,000						31,000,000
Debt discount on notes, net of taxes									12,800,000
Estimated non convertible borrowing rate									10.50%
Repurchased aggregate principal amount in convertible notes									232,800,000				20,200,000
Principal amount repurchased related to convertible notes									155,100,000				30,000,000
Amount of outstanding convertible notes												134,900,000
Estimated fair value of common stock issued									67,900,000																																																	614,000	564,000
Cash Repayment on conversion																164,900,000
Estimated fair value of common stock issued per share																																																										$ 0.01	$ 0.01
Fair value of liability component	48,100,000	49,700,000							156,700,000
Date of first required payment																				Jan. 15, 2013
Interest payable description																				Semi-annually in arrears on January 15 and July 15 of each year
Notes redeemed percentage of aggregate principal amount						35.00%														35.00%
Notes redemption price percentage of the par value																				107.00%
Notes redemption price percentage of the par value due to change of control																				101.00%
Debt instrument maximum allowed dividends per share						$ 0.10														$ 0.10
Outstanding principal amount of the 7.0% Notes	25.00%
Indebtedness with outstanding balance						35,000,000														35,000,000
Acceleration of notes obligation by holders						25.00%
Number of notes payable					3
Notes payable due date					October 2015 and August 2016																								between June 2013 and March 2031
Premium recorded on Notes payable					7,300,000
Remaining unamortized premium balance	700,000	1,200,000			700,000
Benefits and charges related to Cash flow swaps not designated as hedges																															$ 700,000	$ 800,000	$ 4,900,000
Covenants under 2011 Credit facilities																																																Sonic agreed under the 2011 Credit Facilities not to pledge any assets to any third party, subject to certain stated exceptions, including floor plan financing arrangements
Restrictive Covenants Under 2011 Credit facilities and 7 % Notes																				Specifically, the indenture governing Sonic’s 7.0% Notes limits Sonic’s ability to pay quarterly cash dividends on Sonic’s Class A and B common stock in excess of $0.10 per share. Sonic may only pay quarterly cash dividends on Sonic’s Class A and B common stock if Sonic complies with the terms of the indenture governing the 7.0% Notes.																												The 2011 Credit Facilities contain certain negative covenants. Specifically, the 2011 Credit Facilities permit cash dividends on Sonic’s Class A and Class B common stock so long as no event of default (as defined in the 2011 Credit Facilities) has occurred and is continuing and provided that Sonic remains in compliance with all financial covenants under the 2011 Credit Facilities.
Debt Default Description under 9% and 7% Notes						Sonic’s obligations under the 9.0% Notes may be accelerated by the holders of 25% of the outstanding principal amount of the 9.0% Notes then outstanding if certain events of default occur, including: (1) defaults in the payment of principal or interest when due; (2) defaults in the performance, or breach, of Sonic’s covenants under the 9.0% Notes; and (3) certain defaults under other agreements under which Sonic or its subsidiaries have outstanding indebtedness in excess of $35.0 million.														Sonic’s obligations under the 7.0% Notes may be accelerated by the holders of 25% of the outstanding principal amount of the 7.0% Notes then outstanding if certain events of default occur, including: (1) defaults in the payment of principal or interest when due; (2) defaults in the performance, or breach, of Sonic’s covenants under the 7.0% Notes; and (3) certain defaults under other agreements under which Sonic or its subsidiaries have outstanding indebtedness in excess of $35.0 million.