Income Taxes (Details 1)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of the statutory federal income tax rate with Sonic's federal and state overall effective income tax rate from continuing operations
Statutory federal rate	35.00%	35.00%	35.00%
Effective state income tax rate	4.22%	3.92%	4.70%
Valuation allowance adjustments	(3.15%)		(58.69%)
Other	(0.69%)	(0.10%)	0.01%
Effective tax rate	35.38%	38.82%	(18.98%)