Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Cash Flows [Abstract]
Net income	$ 523.0	$ 424.4	$ 403.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	260.9	254.5	227.4
Equity-based compensation expense	43.7	39.2	31.2
Deferred income taxes	(172.7)	(97.2)	(54.5)
Amortization of deferred financing costs, debt premium and debt discount, net	5.2	6.5	6.4
Net loss on extinguishments of long-term debt	57.4	2.1	24.3
Loss from equity investments	0.0	0.0	11.2
Gain on remeasurement of equity investment	0.0	0.0	(98.1)
Mark-to-market (gain) loss on interest rate cap agreements	(0.5)	(2.6)	2.1
Other	0.4	0.4	0.3
Changes in assets and liabilities:
Accounts receivable	(128.4)	(179.9)	(342.6)
Merchandise inventory	8.5	(68.5)	(31.5)
Other assets	(116.4)	(50.1)	(71.2)
Accounts payable-trade	231.5	225.1	100.5
Other current liabilities	51.4	80.2	47.5
Long-term liabilities	13.7	(30.1)	21.4
Net cash provided by operating activities	777.7	604.0	277.5
Cash flows used in investing activities:
Capital expenditures	(81.1)	(63.5)	(90.1)
Premium payments on interest rate cap agreements	0.0	(2.4)	(0.5)
Acquisition of business, net of cash acquired	0.0	0.0	(263.8)
Net cash used in investing activities	(81.1)	(65.9)	(354.4)
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facility	1,560.7	338.8	314.5
Repayments of borrowings under revolving credit facility	(1,560.7)	(338.8)	(314.5)
Repayments of long-term debt	(14.9)	(20.6)	(32.8)
Proceeds from issuance of long-term debt	2,083.0	1,483.0	525.0
Payments to extinguish long-term debt	(2,121.3)	(1,490.4)	(525.3)
Net change in other long-term obligation	(3.8)	15.7	0.0
Payments of debt financing costs	(9.6)	(5.9)	(6.8)
Net change in accounts payable-inventory financing	(84.0)	143.6	95.9
Effective portion of interest rate cap agreements	0.4	0.0	0.0
Proceeds from stock option exercises	13.0	7.4	2.4
Proceeds from Coworker Stock Purchase Plan	10.3	9.3	8.7
Repurchases of common stock	(534.0)	(367.4)	(241.3)
Payment of incentive compensation plan withholding taxes	(49.6)	0.0	(0.6)
Dividends	(106.9)	(78.7)	(52.9)
Principal payments under capital lease obligations	(1.3)	(0.6)	0.0
Net cash (used in) provided by financing activities	(818.7)	(304.6)	(226.5)
Effect of exchange rate changes on cash and cash equivalents	2.6	(7.4)	(3.5)
Net (decrease) increase in cash and cash equivalents	(119.5)	226.1	(306.9)
Cash and cash equivalents – beginning of period	263.7	37.6	344.5
Cash and cash equivalents – end of period	144.2	263.7	37.6
Supplementary disclosure of cash flow information:
Interest paid	(148.5)	(144.3)	(154.6)
Taxes paid, net	$ (275.7)	$ (329.2)	$ (300.2)