Detail of Certain Balance Sheet Accounts (Accounts and Notes Receivable) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts and notes receivable
Total accounts and notes receivable	$ 134,917	$ 112,873
Less allowance for doubtful accounts	(2,404)	(1,645)
Accounts and notes receivable, net	132,513	111,228
Amounts due from manufacturers [Member]
Accounts and notes receivable
Total accounts and notes receivable	66,518	64,039
Parts and service receivables [Member]
Accounts and notes receivable
Total accounts and notes receivable	32,649	17,879
Finance and insurance receivables, net [Member]
Accounts and notes receivable
Total accounts and notes receivable	15,863	16,060
Other [Member]
Accounts and notes receivable
Total accounts and notes receivable	$ 19,887	$ 14,895