Accounts and Notes Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts and notes receivable
Total accounts and notes receivable	$ 191,749	$ 176,260
Less allowance for doubtful accounts	3,138	2,896
Accounts and notes receivable, net	188,611	173,364
Amounts due from manufacturers [Member]
Accounts and notes receivable
Total accounts and notes receivable	109,599	95,754
Parts and service receivables [Member]
Accounts and notes receivable
Total accounts and notes receivable	39,343	35,318
Finance and insurance receivables, net [Member]
Accounts and notes receivable
Total accounts and notes receivable	25,293	24,866
Other [Member]
Accounts and notes receivable
Total accounts and notes receivable	$ 17,514	$ 20,322