Sonic Automotive, Inc. Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Option	Dec. 31, 2012	Dec. 31, 2011
Commitments And Contingencies Disclosure [Abstract]
Lease exit expense	$ 2.9
Lease exit accrued cost	0.3
Remaining lease exit expense	2.6
Operating lease term for dealership facilities, minimum	15 years
Operating lease term for dealership facilities, maximum	20 years
Operating lease number of renewal options, minimum	1
Operating lease number of renewal options, maximum	2
Operating lease period of renewal options	10 years
Percentage of lease facility based on capitalization rates	20.00%
Lease expense for continuing operation	99.6	102.4	103.2
Lease expense for discontinuing operation	1.1	6.2	5.7
Leases, net contingent rent benefit related to decrease in interest rates from continuing operation	2.3	2.3	2.3
Leases net contingent rent benefit related to decrease in interest rates from discontinuing operation	0.6	0.6	0.6
Obligations under subleases, if subleases do not perform	94.1
Estimated minimum lease payment	7.2
Maximum exposure associated with general indemnifications	14.0
General indemnifications minimum expiration period	1 year
General indemnifications maximum expiration period	2 years
Joint venture ownership percentage	50.00%
Contingent liability reserve balance after reduction	2.8
Amount reserved for pending proceedings	$ 1.2	$ 3.4