Business Acquisitions and Dispositions - Revenues and Other Activities Associated with Disposed Dealerships That Remain in Continued Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Business Combinations [Abstract]
Income (loss) from operations	$ (998)	$ 719	$ (1,280)	$ 205
Gain (loss) on disposal	1,057	7,260	955	7,624
Property impairment charges	(10,096)		(10,096)
Pre-tax income (loss)	(10,037)	7,979	(10,421)	7,829
Total revenues	$ 4,504	$ 82,783	$ 10,603	$ 155,232