Supplemental Guarantor Information -Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	$ 369.9	$ 427.8
Capital Expenditures	(19.6)	(11.0)
Net cash used in investing activities	(19.6)	(11.0)
Proceeds from Lines of Credit	44.1	63.4
Repayments of Lines of Credit	(6.1)	(63.4)
Repayments of long-term debt	(3.7)	(6.7)
Proceeds from Issuance of Long-term Debt	2,083.0	0.0
Repayments of Long-term Debt	(2,121.3)	0.0
Payments of Financing Costs	(9.6)	0.0
Net change in accounts payable-inventory financing	(135.7)	(66.5)
Proceeds from stock option exercises	4.4	1.2
Proceeds from Coworker Stock Purchase Plan	2.1	1.9
Stock Repurchased and Retired During Period, Value	(175.4)	(118.0)
Payment of incentive compensation plan withholding taxes, employer portion	(18.3)
Payments of Ordinary Dividends, Common Stock	(25.5)	(18.0)
Repayments of Debt and Capital Lease Obligations		(0.5)
Proceeds from (Payments for) Other Financing Activities	(0.2)	(0.5)
Advances from (to) affiliates	0.0	0.0
Net cash used in financing activities	(362.2)	(206.6)
Effect of exchange rate changes on cash and cash equivalents	(0.1)	0.4
Net increase (decrease) in cash and cash equivalents	(12.0)	210.6
Cash and cash equivalents - beginning of period	263.7	37.6
Cash and cash equivalents - end of period	251.7	248.2
Consolidating Adjustments [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	(26.0)	24.6
Capital Expenditures	0.0	0.0
Net cash used in investing activities	0.0	0.0
Proceeds from Lines of Credit	0.0	0.0
Repayments of Lines of Credit	0.0	0.0
Repayments of long-term debt	0.0	0.0
Proceeds from Issuance of Long-term Debt	0.0
Repayments of Long-term Debt	0.0
Payments of Financing Costs	0.0
Net change in accounts payable-inventory financing	0.0	0.0
Proceeds from stock option exercises	0.0	0.0
Proceeds from Coworker Stock Purchase Plan	0.0	0.0
Stock Repurchased and Retired During Period, Value	0.0	0.0
Payment of incentive compensation plan withholding taxes, employer portion	0.0
Payments of Ordinary Dividends, Common Stock	0.0	0.0
Repayments of Debt and Capital Lease Obligations		0.0
Proceeds from (Payments for) Other Financing Activities	0.0
Advances from (to) affiliates	2.4	(5.0)
Net cash used in financing activities	2.4	(5.0)
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0
Net increase (decrease) in cash and cash equivalents	(23.6)	19.6
Cash and cash equivalents - beginning of period	0.0	(39.4)
Cash and cash equivalents - end of period	(23.6)	(19.8)
Parent Guarantor [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities		0.0
Capital Expenditures		0.0
Net cash used in investing activities	0.0	0.0
Proceeds from Lines of Credit	0.0	0.0
Repayments of Lines of Credit	0.0	0.0
Repayments of long-term debt		0.0
Net change in accounts payable-inventory financing		0.0
Proceeds from stock option exercises		0.0
Proceeds from Coworker Stock Purchase Plan		0.0
Stock Repurchased and Retired During Period, Value		(118.0)
Payments of Ordinary Dividends, Common Stock		(18.0)
Repayments of Debt and Capital Lease Obligations		0.0
Advances from (to) affiliates		136.0
Net cash used in financing activities		0.0
Effect of exchange rate changes on cash and cash equivalents		0.0
Net increase (decrease) in cash and cash equivalents	0.0	0.0
Cash and cash equivalents - beginning of period		0.0
Cash and cash equivalents - end of period	0.0	0.0
Parent Guarantor [Member] | Reportable Legal Entities [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	0.0
Capital Expenditures	0.0
Repayments of long-term debt	0.0
Proceeds from Issuance of Long-term Debt	0.0
Repayments of Long-term Debt	0.0
Payments of Financing Costs	0.0
Net change in accounts payable-inventory financing	0.0
Proceeds from stock option exercises	0.0
Proceeds from Coworker Stock Purchase Plan	0.0
Stock Repurchased and Retired During Period, Value	(175.4)
Payment of incentive compensation plan withholding taxes, employer portion	0.0
Payments of Ordinary Dividends, Common Stock	(25.5)
Proceeds from (Payments for) Other Financing Activities	0.0
Advances from (to) affiliates	200.9
Net cash used in financing activities	0.0
Effect of exchange rate changes on cash and cash equivalents	0.0
Cash and cash equivalents - beginning of period	0.0
Cash and cash equivalents - end of period	0.0
Subsidiary Issuer [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities		(16.8)
Capital Expenditures		(9.9)
Net cash used in investing activities	(14.6)	(9.9)
Proceeds from Lines of Credit		63.4
Repayments of Lines of Credit		(63.4)
Repayments of long-term debt		(3.9)
Net change in accounts payable-inventory financing		0.0
Proceeds from stock option exercises		1.2
Proceeds from Coworker Stock Purchase Plan		1.9
Stock Repurchased and Retired During Period, Value		0.0
Payments of Ordinary Dividends, Common Stock		0.0
Repayments of Debt and Capital Lease Obligations		0.0
Advances from (to) affiliates		167.8
Net cash used in financing activities		167.0
Effect of exchange rate changes on cash and cash equivalents		0.0
Net increase (decrease) in cash and cash equivalents		140.3
Cash and cash equivalents - beginning of period		45.1
Cash and cash equivalents - end of period	204.9	185.4
Subsidiary Issuer [Member] | Reportable Legal Entities [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	24.5
Capital Expenditures	(14.6)
Proceeds from Lines of Credit	38.0
Repayments of Lines of Credit	0.0
Repayments of long-term debt	(3.7)
Proceeds from Issuance of Long-term Debt	2,083.0
Repayments of Long-term Debt	(2,121.3)
Payments of Financing Costs	(9.6)
Net change in accounts payable-inventory financing	(0.9)
Proceeds from stock option exercises	4.4
Proceeds from Coworker Stock Purchase Plan	2.1
Stock Repurchased and Retired During Period, Value	0.0
Payment of incentive compensation plan withholding taxes, employer portion	(10.4)
Payments of Ordinary Dividends, Common Stock	0.0
Proceeds from (Payments for) Other Financing Activities	0.0
Advances from (to) affiliates	(9.3)
Net cash used in financing activities	(27.7)
Effect of exchange rate changes on cash and cash equivalents	0.0
Net increase (decrease) in cash and cash equivalents	(17.8)
Cash and cash equivalents - beginning of period	222.7
Cash and cash equivalents - end of period	204.9
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	333.2	377.9
Capital Expenditures	(2.4)	(0.5)
Net cash used in investing activities	(2.4)	(0.5)
Proceeds from Lines of Credit	0.0	0.0
Repayments of Lines of Credit	0.0	0.0
Repayments of long-term debt	0.0	0.0
Proceeds from Issuance of Long-term Debt	0.0
Repayments of Long-term Debt	0.0
Payments of Financing Costs	0.0
Net change in accounts payable-inventory financing	(132.2)	(72.9)
Proceeds from stock option exercises	0.0	0.0
Proceeds from Coworker Stock Purchase Plan	0.0	0.0
Stock Repurchased and Retired During Period, Value	0.0	0.0
Payment of incentive compensation plan withholding taxes, employer portion	(7.7)
Payments of Ordinary Dividends, Common Stock	0.0	0.0
Repayments of Debt and Capital Lease Obligations		0.0
Proceeds from (Payments for) Other Financing Activities	0.0
Advances from (to) affiliates	(194.0)	(304.5)
Net cash used in financing activities	(333.9)	(377.4)
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0
Net increase (decrease) in cash and cash equivalents	(3.1)	0.0
Cash and cash equivalents - beginning of period	3.1	0.0
Cash and cash equivalents - end of period	0.0	0.0
Non-Guarantor Subsidiaries [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities		42.1
Capital Expenditures		(0.6)
Net cash used in investing activities	(2.6)	(0.6)
Proceeds from Lines of Credit		0.0
Repayments of Lines of Credit		0.0
Repayments of long-term debt		(2.8)
Net change in accounts payable-inventory financing		6.4
Proceeds from stock option exercises		0.0
Proceeds from Coworker Stock Purchase Plan		0.0
Stock Repurchased and Retired During Period, Value		0.0
Payments of Ordinary Dividends, Common Stock	0.0	0.0
Repayments of Debt and Capital Lease Obligations		(0.5)
Advances from (to) affiliates		5.7
Net cash used in financing activities		8.8
Effect of exchange rate changes on cash and cash equivalents		0.4
Net increase (decrease) in cash and cash equivalents		50.7
Cash and cash equivalents - beginning of period		31.9
Cash and cash equivalents - end of period	70.4	82.6
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	38.2
Capital Expenditures	(2.6)
Proceeds from Lines of Credit	6.1
Repayments of Lines of Credit	(6.1)
Repayments of long-term debt	0.0
Proceeds from Issuance of Long-term Debt	0.0
Repayments of Long-term Debt	0.0
Payments of Financing Costs	0.0
Net change in accounts payable-inventory financing	(2.6)
Proceeds from stock option exercises	0.0
Proceeds from Coworker Stock Purchase Plan	0.0
Stock Repurchased and Retired During Period, Value	0.0
Payment of incentive compensation plan withholding taxes, employer portion	(0.2)
Proceeds from (Payments for) Other Financing Activities	(0.2)
Advances from (to) affiliates	0.0
Net cash used in financing activities	(3.0)
Effect of exchange rate changes on cash and cash equivalents	(0.1)
Net increase (decrease) in cash and cash equivalents	32.5
Cash and cash equivalents - beginning of period	37.9
Cash and cash equivalents - end of period	70.4
Co-Issuer [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities		0.0
Capital Expenditures		0.0
Net cash used in investing activities	0.0	0.0
Proceeds from Lines of Credit	0.0	0.0
Repayments of Lines of Credit	0.0	0.0
Repayments of long-term debt		0.0
Net change in accounts payable-inventory financing		0.0
Proceeds from stock option exercises		0.0
Proceeds from Coworker Stock Purchase Plan		0.0
Stock Repurchased and Retired During Period, Value		0.0
Payments of Ordinary Dividends, Common Stock		0.0
Repayments of Debt and Capital Lease Obligations		0.0
Advances from (to) affiliates		0.0
Net cash used in financing activities	0.0	0.0
Effect of exchange rate changes on cash and cash equivalents		0.0
Net increase (decrease) in cash and cash equivalents		0.0
Cash and cash equivalents - beginning of period		0.0
Cash and cash equivalents - end of period	0.0	$ 0.0
Co-Issuer [Member] | Reportable Legal Entities [Member]
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	0.0
Capital Expenditures	0.0
Repayments of long-term debt	0.0
Proceeds from Issuance of Long-term Debt	0.0
Repayments of Long-term Debt	0.0
Payments of Financing Costs	0.0
Net change in accounts payable-inventory financing	0.0
Proceeds from stock option exercises	0.0
Proceeds from Coworker Stock Purchase Plan	0.0
Stock Repurchased and Retired During Period, Value	0.0
Payment of incentive compensation plan withholding taxes, employer portion	0.0
Payments of Ordinary Dividends, Common Stock	0.0
Proceeds from (Payments for) Other Financing Activities	0.0
Advances from (to) affiliates	0.0
Effect of exchange rate changes on cash and cash equivalents	0.0
Net increase (decrease) in cash and cash equivalents	0.0
Cash and cash equivalents - beginning of period	0.0
Cash and cash equivalents - end of period	$ 0.0