CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net income	$ 681.3	$ 461.1
Adjustments to reconcile net income to net cash used for operating activities:
Depreciation and amortization	80.2	57.1
Stock-based compensation	23.1	17.2
(Gain) loss on disposal of other assets	(0.6)	0.1
(Gain) loss on disposal of franchise	(13.1)	5.2
Unrealized investment loss (gain)	33.0	(0.9)
Deferred income taxes	16.6	31.8
Amortization of operating lease right-of-use assets	19.3	16.5
(Increase) decrease (net of acquisitions and dispositions):
Accounts receivable, net	(76.4)	(185.0)
Inventories	(507.0)	663.1
Other assets	(628.3)	(95.5)
Increase (decrease) (net of acquisitions and dispositions):
Floor plan notes payable	56.9	47.0
Trade payables	32.6	97.4
Accrued liabilities	(16.8)	144.3
Other long-term liabilities and deferred revenue	36.1	11.6
Net cash provided by (used in) operating activities	(263.1)	1,271.0
Cash flows from investing activities:
Capital expenditures	(136.6)	(113.0)
Proceeds from sales of assets	16.5	0.0
Cash paid for other investments	(9.3)	(9.9)
Cash paid for acquisitions, net of cash acquired	(706.0)	(1,741.9)
Proceeds from sales of stores	52.7	43.7
Net cash used in investing activities	(782.7)	(1,821.1)
Cash flows from financing activities:
Borrowings (repayments) on floor plan notes payable, net: non-trade	243.5	(571.6)
Borrowings on lines of credit	6,047.8	1,454.9
Repayments on lines of credit	(4,543.9)	(1,519.5)
Principal payments on long-term debt and finance lease liabilities, scheduled	(96.0)	(12.6)
Principal payments on long-term debt and finance lease liabilities, other	(60.3)	(65.0)
Proceeds from issuance of long-term debt	26.7	817.5
Payment of debt issuance costs	(1.5)	(10.6)
Proceeds from issuance of common stock	18.7	1,120.0
Repurchase of common stock	(623.4)	(15.9)
Dividends paid	(22.2)	(17.5)
Payment of contingent consideration related to acquisitions	(3.7)	(1.4)
Other financing activity	(1.1)	0.0
Net cash provided by financing activities	984.6	1,178.3
Effect of exchange rate changes on cash and cash equivalents	(0.4)	0.0
Increase (decrease) in cash, restricted cash, and cash equivalents	(61.6)	628.3
Cash, restricted cash, and cash equivalents at beginning of year	178.5	162.4
Cash, restricted cash, and cash equivalents at end of period	116.9	790.7
Reconciliation of cash, restricted cash, and cash equivalents to the consolidated balance sheets
Cash, restricted cash, and cash equivalents	64.4	780.9
Restricted cash from collections on auto loans receivable and customer deposits	48.8	9.8
Cash, restricted cash, and cash equivalents	113.2	790.7
Restricted cash on deposit in reserve accounts, included in other non-current assets	3.7	0.0
Total cash, restricted cash, and cash equivalents reported in the Consolidated Statements of Cash Flows	116.9	790.7
Supplemental cash flow information:
Cash paid during the period for interest	71.9	57.2
Cash paid during the period for income taxes, net	259.2	129.3
Floor plan debt paid in connection with store disposals	0.0	8.7
Non-cash activities:
Debt issued in connection with acquisitions	0.0	225.6
Debt assumed in connection with acquisitions	0.0	4.0
Acquisition of finance leases in connection with acquisitions	59.0	0.0
Right-of-use assets obtained in exchange for lease liabilities	16.5	8.1
Unsettled repurchases of common stock	$ 2.2	$ 0.0