Inventories - Components of Inventories (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Inventory Disclosure [Abstract]
New vehicles	$ 856,393	$ 938,263
Used vehicles	187,071	171,909
Service loaners	106,915	108,136
Parts, accessories and other	60,645	63,830
Subtotal	1,211,024	1,282,138
Less inventories classified as assets held for sale	(7,630)
Net inventories	$ 1,203,394	$ 1,282,138