Sonic Automotive, Inc. Quarterly report pursuant to Section 13 or 15(d)

Business Acquisitions and Dispositions - Additional Information (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($) Business	Sep. 30, 2019 USD ($) Business	Sep. 30, 2018 USD ($) Business
Business Combinations [Abstract]
Number of acquired franchises \| Business		0
Business Acquisition [Line Items]
Number of franchises disposed \| Business		4	4
Net cash generated from disposition \| $		$ 130,100
Proceeds from sales of dealerships \| $		$ 130,086	$ 121,859
Luxury franchise
Business Acquisition [Line Items]
Number of franchises terminated \| Business	1		2
Mid-line import franchise
Business Acquisition [Line Items]
Net cash generated from disposition \| $	$ 121,900