Supplemental Guarantor Information - Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 144.2	$ 263.7	$ 37.6	$ 344.5
Accounts receivable, net	2,320.5	2,168.6
Merchandise inventory	449.5	452.0
Miscellaneous receivables	336.5	234.9
Prepaid expenses and other	127.4	118.9
Total current assets	3,378.1	3,238.1
Property and equipment, net	161.1	163.7
Goodwill	2,479.6	2,455.0	2,500.4	2,217.6
Other intangible assets, net	897.0	1,055.6
Other assets	40.8	36.0
Investment in and advances to subsidiaries	0.0	0.0
Total Assets	6,956.6	6,948.4
Current liabilities:
Accounts payable-trade	1,317.7	1,072.9
Accounts payable-inventory financing	498.0	580.4
Current maturities of long-term debt	25.5	18.5
Deferred revenue	194.0	172.6
Accrued expenses	479.4	436.3
Total current liabilities	2,514.6	2,280.7
Long-term liabilities:
Debt	3,210.0	3,215.9
Deferred income taxes	196.3	369.2
Other liabilities	52.8	37.1
Total long-term liabilities	3,459.1	3,622.2
Total stockholders’ equity	982.9	1,045.5	1,095.9	936.5
Total Liabilities and Stockholders’ Equity	6,956.6	6,948.4
Reportable Legal Entities | Parent Guarantor
Current assets:
Cash and cash equivalents	0.0	0.0	0.0	0.0
Accounts receivable, net	0.0	0.0
Merchandise inventory	0.0	0.0
Miscellaneous receivables	0.0	0.0
Prepaid expenses and other	0.0	0.0
Total current assets	0.0	0.0
Property and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Other intangible assets, net	0.0	0.0
Other assets	1.7	3.2
Investment in and advances to subsidiaries	981.2	1,042.3
Total Assets	982.9	1,045.5
Current liabilities:
Accounts payable-trade	0.0	0.0
Accounts payable-inventory financing	0.0	0.0
Current maturities of long-term debt	0.0	0.0
Deferred revenue	0.0	0.0
Accrued expenses	0.0	0.0
Total current liabilities	0.0	0.0
Long-term liabilities:
Debt	0.0	0.0
Deferred income taxes	0.0	0.0
Other liabilities	0.0	0.0
Total long-term liabilities	0.0	0.0
Total stockholders’ equity	982.9	1,045.5
Total Liabilities and Stockholders’ Equity	982.9	1,045.5
Reportable Legal Entities | Subsidiary Issuer
Current assets:
Cash and cash equivalents	113.7	222.7	45.1	346.4
Accounts receivable, net	0.0	0.0
Merchandise inventory	0.0	0.0
Miscellaneous receivables	103.9	92.6
Prepaid expenses and other	18.0	14.3
Total current assets	235.6	329.6
Property and equipment, net	95.0	105.6
Goodwill	751.8	751.8
Other intangible assets, net	280.1	291.5
Other assets	30.7	19.4
Investment in and advances to subsidiaries	3,063.5	3,026.5
Total Assets	4,456.7	4,524.4
Current liabilities:
Accounts payable-trade	42.5	25.9
Accounts payable-inventory financing	1.0	1.2
Current maturities of long-term debt	14.9	14.9
Deferred revenue	0.0	0.0
Accrued expenses	173.3	173.9
Total current liabilities	231.7	215.9
Long-term liabilities:
Debt	3,134.2	3,136.3
Deferred income taxes	66.5	99.1
Other liabilities	43.1	30.8
Total long-term liabilities	3,243.8	3,266.2
Total stockholders’ equity	981.2	1,042.3
Total Liabilities and Stockholders’ Equity	4,456.7	4,524.4
Reportable Legal Entities | Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	0.0	3.1	0.0	0.0
Accounts receivable, net	2,007.7	1,904.9
Merchandise inventory	375.7	390.6
Miscellaneous receivables	205.0	130.1
Prepaid expenses and other	61.4	69.0
Total current assets	2,649.8	2,497.7
Property and equipment, net	43.5	49.3
Goodwill	1,439.0	1,439.0
Other intangible assets, net	424.5	565.1
Other assets	217.3	248.2
Investment in and advances to subsidiaries	0.0	0.0
Total Assets	4,774.1	4,799.3
Current liabilities:
Accounts payable-trade	1,112.1	895.3
Accounts payable-inventory financing	480.9	559.5
Current maturities of long-term debt	3.8	3.6
Deferred revenue	104.5	100.8
Accrued expenses	222.3	214.8
Total current liabilities	1,923.6	1,774.0
Long-term liabilities:
Debt	8.3	12.1
Deferred income taxes	100.1	205.4
Other liabilities	4.6	3.6
Total long-term liabilities	113.0	221.1
Total stockholders’ equity	2,737.5	2,804.2
Total Liabilities and Stockholders’ Equity	4,774.1	4,799.3
Reportable Legal Entities | Non-Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	32.4	37.9	31.9	24.6
Accounts receivable, net	312.8	263.7
Merchandise inventory	73.8	61.4
Miscellaneous receivables	27.6	12.2
Prepaid expenses and other	48.0	35.6
Total current assets	494.6	410.8
Property and equipment, net	22.6	8.8
Goodwill	288.8	264.2
Other intangible assets, net	192.4	199.0
Other assets	2.6	1.5
Investment in and advances to subsidiaries	0.0	0.0
Total Assets	1,001.0	884.3
Current liabilities:
Accounts payable-trade	165.0	151.7
Accounts payable-inventory financing	16.1	19.7
Current maturities of long-term debt	6.8	0.0
Deferred revenue	89.5	71.8
Accrued expenses	83.8	47.7
Total current liabilities	361.2	290.9
Long-term liabilities:
Debt	67.5	67.5
Deferred income taxes	31.4	67.9
Other liabilities	214.9	235.7
Total long-term liabilities	313.8	371.1
Total stockholders’ equity	326.0	222.3
Total Liabilities and Stockholders’ Equity	1,001.0	884.3
Reportable Legal Entities | Co-Issuer
Current assets:
Cash and cash equivalents	0.0	0.0	0.0	0.0
Accounts receivable, net	0.0	0.0
Merchandise inventory	0.0	0.0
Miscellaneous receivables	0.0	0.0
Prepaid expenses and other	0.0	0.0
Total current assets	0.0	0.0
Property and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Other intangible assets, net	0.0	0.0
Other assets	0.0	0.0
Investment in and advances to subsidiaries	0.0	0.0
Total Assets	0.0	0.0
Current liabilities:
Accounts payable-trade	0.0	0.0
Accounts payable-inventory financing	0.0	0.0
Current maturities of long-term debt	0.0	0.0
Deferred revenue	0.0	0.0
Accrued expenses	0.0	0.0
Total current liabilities	0.0	0.0
Long-term liabilities:
Debt	0.0	0.0
Deferred income taxes	0.0	0.0
Other liabilities	0.0	0.0
Total long-term liabilities	0.0	0.0
Total stockholders’ equity	0.0	0.0
Total Liabilities and Stockholders’ Equity	0.0	0.0
Consolidating Adjustments
Current assets:
Cash and cash equivalents	(1.9)	0.0	$ (39.4)	$ (26.5)
Accounts receivable, net	0.0	0.0
Merchandise inventory	0.0	0.0
Miscellaneous receivables	0.0	0.0
Prepaid expenses and other	0.0	0.0
Total current assets	(1.9)	0.0
Property and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Other intangible assets, net	0.0	0.0
Other assets	(211.5)	(236.3)
Investment in and advances to subsidiaries	(4,044.7)	(4,068.8)
Total Assets	(4,258.1)	(4,305.1)
Current liabilities:
Accounts payable-trade	(1.9)	0.0
Accounts payable-inventory financing	0.0	0.0
Current maturities of long-term debt	0.0	0.0
Deferred revenue	0.0	0.0
Accrued expenses	0.0	(0.1)
Total current liabilities	(1.9)	(0.1)
Long-term liabilities:
Debt	0.0	0.0
Deferred income taxes	(1.7)	(3.2)
Other liabilities	(209.8)	(233.0)
Total long-term liabilities	(211.5)	(236.2)
Total stockholders’ equity	(4,044.7)	(4,068.8)
Total Liabilities and Stockholders’ Equity	$ (4,258.1)	$ (4,305.1)