CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities:
Net income	$ 1,192,700,000	$ 545,300,000	$ 435,100,000
Adjustments to reconcile net income to net cash from continuing operating activities:
Depreciation	121,500,000	115,500,000	109,600,000
Loss on investment	11,400,000	0	0
Earnings of equity method investments	(234,900,000)	(115,000,000.0)	(94,600,000)
Income from discontinued operations, net of tax	(1,300,000)	(400,000)	(300,000)
Deferred income taxes	184,800,000	194,300,000	92,000,000.0
Debt redemption costs	17,000,000.0	8,600,000	0
Changes in operating assets and liabilities:
Accounts receivable	75,600,000	152,700,000	(30,900,000)
Inventories	402,600,000	805,400,000	(117,800,000)
Floor plan notes payable	(628,600,000)	(611,000,000.0)	83,900,000
Accounts payable and accrued expenses	139,000,000.0	125,000,000.0	71,400,000
Other	12,200,000	(18,900,000)	(30,100,000)
Net cash provided by continuing operating activities	1,292,000,000	1,201,500,000	518,300,000
Investing Activities:
Purchase of equipment and improvements	(248,900,000)	(185,900,000)	(245,300,000)
Proceeds from sale of dealerships	4,300,000	40,600,000	22,800,000
Proceeds from sale-leaseback transactions	0	0	18,900,000
Proceeds from sale of equipment and improvements	54,900,000	19,800,000	8,600,000
Acquisitions net, including repayment of sellers’ floor plan notes payable of $43.0, $0.0, and $138.5, respectively	(431,800,000)	0	(326,900,000)
Other	(1,600,000)	(11,000,000.0)	(10,800,000)
Net cash used in continuing investing activities	(623,100,000)	(136,500,000)	(532,700,000)
Financing Activities:
Proceeds from borrowings under U.S. credit agreement revolving credit line	1,856,000,000	1,797,000,000	1,808,000,000
Repayments under U.S. credit agreement revolving credit line	(1,964,000,000)	(1,734,000,000)	(1,793,000,000)
Net (repayments) borrowings of other long-term debt	(104,200,000)	(144,400,000)	115,400,000
Net borrowings (repayments) of floor plan notes payable — non-trade	38,900,000	(230,200,000)	177,500,000
Payments for contingent consideration	0	(31,600,000)	0
Repurchases of common stock	(280,600,000)	(29,400,000)	(169,200,000)
Dividends	(142,500,000)	(68,100,000)	(130,800,000)
Payment of debt issuance costs	(6,300,000)	(8,100,000)	(400,000)
Other	(12,800,000)	(5,100,000)	(4,900,000)
Net cash (used in) provided by continuing financing activities	(615,500,000)	(1,053,900,000)	2,600,000
Discontinued operations:
Net cash provided by discontinued operating activities	1,300,000	300,000	300,000
Net cash provided by discontinued operations	1,300,000	300,000	300,000
Effect of exchange rate changes on cash and cash equivalents	(3,500,000)	10,000,000.0	200,000
Net change in cash and cash equivalents	51,200,000	21,400,000	(11,300,000)
Cash and cash equivalents, beginning of period	49,500,000	28,100,000	39,400,000
Cash and cash equivalents, end of period	100,700,000	49,500,000	28,100,000
Cash paid for:
Interest	95,300,000	168,500,000	204,900,000
Income taxes	160,100,000	17,900,000	92,400,000
Non cash activities:
Contingent consideration	0	0	10,600,000
3.50% senior subordinated notes due 2025
Financing Activities:
Issuance of senior subordinated notes	0	550,000,000.0	0
3.75% senior subordinated notes due 2029
Financing Activities:
Issuance of senior subordinated notes	500,000,000.0	0	0
3.75% senior subordinated notes due 2020
Financing Activities:
Repayment of senior subordinated notes	0	(300,000,000.0)	0
5.375% senior subordinated notes due 2024
Financing Activities:
Repayment of senior subordinated notes	0	(300,000,000.0)	0
5.50% senior subordinated notes due 2026 redeemed June 24, 2021
Financing Activities:
Repayment of senior subordinated notes	(500,000,000.0)	0	0
5.75% senior subordinated notes due 2022
Financing Activities:
Repayment of senior subordinated notes	$ 0	$ (550,000,000.0)	$ 0