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

Inventories and Related Notes Payable - Floor Plan - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Inventory Disclosure [Abstract]
Average interest rate for new vehicle floor plan facilities, for continuing operations and discontinued operations	1.86%	2.02%	2.39%
Amount recognized as reduction in cost of sales for continuing and discontinued operations	$ 37.9	$ 33.0	$ 26.7
Average interest rate for used vehicle floor plan facilities, for continuing operations and discontinued operations	2.78%	2.80%	2.71%