Summary of Significant Accounting Policies - Cumulative Effect of Adjustments for Adoption of ASC 606 (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenues:
Revenues	$ 2,786,798,000	$ 2,308,056,000
Cost of Sales:
Cost of Sales	(2,385,905,000)	(1,957,478,000)
Operating income (loss)	87,850,000	(221,875,000)
Assets:
Receivables, net	373,518,000		$ 371,666,000
Liabilities:
Other accrued liabilities	295,331,000		279,477,000
Deferred income taxes	771,000		345,000
Stockholders' Equity:
Retained Earnings (Accumulated Deficit)	771,864,000		721,770,000
Parts, service and collision repair
Revenues:
Revenues	320,914,000	334,680,000
Cost of Sales:
Cost of Sales	(165,864,000)	(176,782,000)
Finance, insurance and other, net
Revenues:
Revenues	144,661,000	$ 115,292,000
ASU 2014-09 | Finance, insurance and other, net
Assets:
Contract assets	$ 14,500,000		$ 21,700,000