Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022		Dec. 31, 2021	Dec. 31, 2020
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES:
Net income	$ 1,377.4		$ 1,373.0	$ 381.6
Adjustments to reconcile net income to net cash provided by operating activities:
Loss from discontinued operations	0.3		0.3	0.2
Depreciation and amortization	200.3		193.3	198.9
Amortization of debt issuance costs and accretion of debt discounts	7.2		4.9	4.7
Stock-based compensation expense	31.5		35.0	30.2
Provision for credit losses on auto loans receivable	43.8	[1]	0.0	0.0
Deferred income tax provision (benefit)	1.3		(17.4)	(38.9)
Net gain on asset sales and dispositions	(16.3)		(18.1)	(7.9)
Goodwill impairment	0.0		0.0	318.3
Franchise rights impairment	0.0		0.0	57.5
Other non-cash impairment charges	1.6		3.2	14.7
Gain on equity investments	(2.9)		(10.9)	(131.5)
Loss (gain) on corporate-owned life insurance asset	19.4		(12.7)	(12.3)
Other	0.0		(0.6)	1.3
(Increase) decrease, net of effects from business combinations and divestitures:
Receivables	(129.2)		114.9	70.0
Inventory	(175.5)		800.4	703.6
Other assets	(58.4)		92.2	85.6
Increase (decrease), net of effects from business combinations and divestitures:
Vehicle floorplan payable-trade	461.1		(1,059.7)	(579.3)
Accounts payable	(68.9)		57.2	47.7
Other liabilities	(24.3)		73.0	63.2
Net cash provided by continuing operations	1,668.4		1,628.0	1,207.6
Net cash used in discontinued operations	(0.3)		(0.3)	0.0
Net cash provided by operating activities	1,668.1		1,627.7	1,207.6
CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES:
Purchases of property and equipment	(329.0)		(215.7)	(156.0)
Proceeds from the disposal of assets held for sale	22.8		37.1	16.4
Cash used in business acquisitions, net of cash acquired	(191.6)		(432.7)	(0.4)
Cash received from business divestitures, net of cash relinquished	55.2		48.7	9.0
Originations of auto loans receivable acquired through third-party dealers	(56.0)		0.0	0.0
Collections on auto loans receivable acquired through third-party dealers	36.4		0.0	0.0
Proceeds from Sale of Equity Securities	1.8		109.4	105.4
Investment in equity securities	(12.0)		(5.5)	(50.0)
Other	(6.9)		(1.6)	1.9
Net cash used in continuing operations	(479.3)		(460.3)	(73.7)
Net cash used in discontinued operations	0.0		0.0	0.0
Net cash used in investing activities	(479.3)		(460.3)	(73.7)
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Repurchases of common stock	(1,699.5)		(2,318.2)	(367.2)
Proceeds from revolving credit facilities	0.0		0.0	1,110.0
Payments of revolving credit facilities	0.0		0.0	(1,110.0)
Net proceeds from (payments of) commercial paper	(290.0)		340.0	(170.0)
Proceeds from non-recourse debt	40.7		0.0	0.0
Payments of non-recourse debt	(35.6)		0.0	0.0
Payment of debt issuance costs	(7.1)		(8.0)	(11.0)
Net proceeds from (payments of) vehicle floorplan payable - non-trade	178.6		(263.9)	(233.3)
Payment of other debt obligations	(12.0)		(10.9)	(17.2)
Proceeds from the exercise of stock options	3.4		54.5	52.7
Payments of tax withholdings for stock-based awards	(31.3)		(18.0)	(8.1)
Net cash used in continuing operations	(1,154.0)		(1,676.5)	(606.7)
Net cash used in discontinued operations	0.0		0.0	0.0
Net cash used in financing activities	(1,154.0)		(1,676.5)	(606.7)
INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	34.8		(509.1)	527.2
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH at beginning of year	60.6		569.7	42.5
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH at end of year	95.4		60.6	569.7
Senior Notes at Three Point Eight Five Percent Due 2032
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Proceeds from Senior Notes	698.8		0.0	0.0
Senior Notes at One Point Nine Five Percent Due 2028
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Proceeds from Senior Notes	0.0		399.2	0.0
Senior Notes at Two Point Four Percent Due 2031
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Proceeds from Senior Notes	0.0		448.8	0.0
Senior Notes at Four Point Seven Five Percent Due 2030
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Proceeds from Senior Notes	0.0		0.0	497.4
Senior Notes at Three Point Three Five Percent Due 2021
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Payment of Senior Notes	0.0		(300.0)	0.0
Senior Notes at Five Point Five Percent Due 2020
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Payment of Senior Notes	$ 0.0		$ 0.0	$ (350.0)

[1] (1) Includes initial credit loss expense of $34.2 million associated with the auto loan portfolio acquired in the acquisition of CIG Financial on October 1, 2022.