Unaudited Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES:
Net income	$ 95.9	$ 111.5
Adjustments to reconcile net income to net cash provided by operating activities:
Loss from discontinued operations	0.3	0.2
Depreciation and amortization	34.8	28.7
Amortization of debt issuance costs and accretion of debt discounts	1.3	1.1
Stock-based compensation expense	15.3	11.1
Deferred income tax provision	4.8	2.7
Net gain related to business/property dispositions	(6.1)	(1.5)
Non-cash impairment charges	0.9	0.2
Excess tax benefit from stock-based awards	(0.6)	(8.1)
Other	3.8	(0.8)
(Increase) decrease, net of effects from business combinations and divestitures:
Receivables	161.2	38.5
Inventory	(146.5)	(23.0)
Other assets	(23.7)	1.4
Increase (decrease), net of effects from business combinations and divestitures:
Vehicle floorplan payable - trade, net	13.7	(43.6)
Accounts payable	2.5	26.6
Other liabilities	40.8	54.8
Net cash provided by continuing operations	198.4	199.8
Net cash used in discontinued operations	(0.2)	(0.2)
Net cash provided by operating activities	198.2	199.6
CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES:
Purchases of property and equipment	(54.7)	(66.4)
Property operating lease buy-outs	(5.0)	0.0
Proceeds from the sale of property and equipment	0.0	0.2
Cash received from business divestitures, net of cash relinquished	6.1	15.7
Cash used in business acquisitions, net of cash acquired	(256.6)	(27.7)
Other	(0.5)	(1.4)
Net cash used in continuing operations	(310.7)	(79.6)
Net cash used in discontinued operations	0.0	0.0
Net cash used in investing activities	(310.7)	(79.6)
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Repurchases of common stock	(371.1)	(9.6)
Proceeds from revolving credit facility	440.0	540.0
Payments of revolving credit facility	(440.0)	(615.0)
Net proceeds from commercial paper	326.5	0.0
Net proceeds from (payments of) vehicle floorplan payable - non-trade	132.8	(54.1)
Payments of mortgage facility	(2.5)	(2.4)
Payments of capital leases and other debt obligations	(0.7)	(0.7)
Proceeds from the exercise of stock options	0.6	12.4
Excess tax benefit from stock-based awards	0.6	8.1
Net cash provided by (used in) continuing operations	86.2	(121.3)
Net cash used in discontinued operations	0.0	0.0
Net cash provided by (used in) financing activities	86.2	(121.3)
DECREASE IN CASH AND CASH EQUIVALENTS	(26.3)	(1.3)
CASH AND CASH EQUIVALENTS at beginning of period	74.1	75.4
CASH AND CASH EQUIVALENTS at end of period	$ 47.8	$ 74.1