Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries - Supplemental Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 109.9	$ 788.8
Restricted cash	34.1	29.0
Accounts receivable, net	554.1	540.9
Notes receivable, net	132.2	143.5
Inventories	231.2	243.1
Prepaid expenses, deposits and other current assets	249.7	131.1
Property and equipment, net	505.3	568.2
Investment in subsidiaries	0.0	0.0
Goodwill	3,372.5	2,956.1
Intangible assets, net	1,903.0	1,604.6
Intercompany balances	0.0	0.0
Software, net	327.8	339.4
Other assets	317.4	380.6
Total assets	7,737.2	7,725.3
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	50.4	40.3
Other current liabilities	705.9	699.5
Long-term debt, excluding current portion	8,794.0	8,736.3
Other long-term liabilities	383.0	276.2
Intercompany balances	0.0	0.0
Stockholders' (deficit) equity	(2,196.1)	(2,027.0)
Total liabilities and stockholders' (deficit) equity	7,737.2	7,725.3
Non-current restricted cash	15.7	16.3
Reportable Legal Entities | SGI (Issuer)
Assets
Cash and cash equivalents	0.0	0.0
Restricted cash	0.7	0.6
Accounts receivable, net	65.0	68.1
Notes receivable, net	0.0	0.0
Inventories	28.0	40.7
Prepaid expenses, deposits and other current assets	63.5	30.3
Property and equipment, net	94.8	91.5
Investment in subsidiaries	902.7	867.9
Goodwill	240.2	240.3
Intangible assets, net	34.7	34.9
Intercompany balances	5,832.2	5,889.8
Software, net	31.0	24.7
Other assets	421.1	388.8
Total assets	7,713.9	7,677.6
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	41.7	32.8
Other current liabilities	180.0	199.0
Long-term debt, excluding current portion	8,791.4	8,733.0
Other long-term liabilities	30.9	11.3
Intercompany balances	0.0	0.0
Stockholders' (deficit) equity	(1,330.1)	(1,298.5)
Total liabilities and stockholders' (deficit) equity	7,713.9	7,677.6
Reportable Legal Entities | SGC (Parent)
Assets
Cash and cash equivalents	40.7	732.6
Restricted cash	0.0	0.0
Accounts receivable, net	0.0	0.4
Notes receivable, net	0.0	0.0
Inventories	0.0	0.0
Prepaid expenses, deposits and other current assets	11.7	6.5
Property and equipment, net	26.9	28.8
Investment in subsidiaries	3,063.8	3,098.7
Goodwill	0.0	0.0
Intangible assets, net	13.3	15.7
Intercompany balances	0.0	0.0
Software, net	65.0	67.2
Other assets	234.7	234.4
Total assets	3,456.1	4,184.3
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	0.0	0.0
Other current liabilities	87.8	67.6
Long-term debt, excluding current portion	0.0	0.0
Other long-term liabilities	128.3	68.8
Intercompany balances	5,436.1	6,074.9
Stockholders' (deficit) equity	(2,196.1)	(2,027.0)
Total liabilities and stockholders' (deficit) equity	3,456.1	4,184.3
Reportable Legal Entities | Guarantor Subsidiaries
Assets
Cash and cash equivalents	0.0	0.0
Restricted cash	29.2	28.3
Accounts receivable, net	190.3	192.6
Notes receivable, net	115.2	121.1
Inventories	91.2	91.8
Prepaid expenses, deposits and other current assets	95.4	41.6
Property and equipment, net	228.1	295.6
Investment in subsidiaries	1,106.4	987.7
Goodwill	1,886.0	1,880.4
Intangible assets, net	1,299.0	1,335.3
Intercompany balances	0.0	0.0
Software, net	180.3	199.0
Other assets	54.5	62.0
Total assets	5,275.6	5,235.4
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	0.0	0.0
Other current liabilities	230.7	254.2
Long-term debt, excluding current portion	0.0	0.0
Other long-term liabilities	620.9	650.3
Intercompany balances	59.7	37.4
Stockholders' (deficit) equity	4,364.3	4,293.5
Total liabilities and stockholders' (deficit) equity	5,275.6	5,235.4
Non-current restricted cash	15.0	16.1
Reportable Legal Entities | Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents	74.8	59.4
Restricted cash	4.2	0.1
Accounts receivable, net	300.0	279.8
Notes receivable, net	17.0	22.4
Inventories	135.4	131.8
Prepaid expenses, deposits and other current assets	80.3	52.7
Property and equipment, net	182.6	179.9
Investment in subsidiaries	0.0	0.0
Goodwill	1,246.3	835.4
Intangible assets, net	556.0	218.7
Intercompany balances	0.0	222.5
Software, net	51.5	48.5
Other assets	214.6	270.3
Total assets	2,862.7	2,321.5
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	8.7	7.5
Other current liabilities	245.3	206.4
Long-term debt, excluding current portion	2.6	3.3
Other long-term liabilities	202.3	110.9
Intercompany balances	336.4	0.0
Stockholders' (deficit) equity	2,067.4	1,993.4
Total liabilities and stockholders' (deficit) equity	2,862.7	2,321.5
Non-current restricted cash	0.7	0.7
Eliminating Entries
Assets
Cash and cash equivalents	(5.6)	(3.2)
Restricted cash	0.0	0.0
Accounts receivable, net	(1.2)	0.0
Notes receivable, net	0.0	0.0
Inventories	(23.4)	(21.2)
Prepaid expenses, deposits and other current assets	(1.2)	0.0
Property and equipment, net	(27.1)	(27.6)
Investment in subsidiaries	(5,072.9)	(4,954.3)
Goodwill	0.0	0.0
Intangible assets, net	0.0	0.0
Intercompany balances	(5,832.2)	(6,112.3)
Software, net	0.0	0.0
Other assets	(607.5)	(574.9)
Total assets	(11,571.1)	(11,693.5)
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	0.0	0.0
Other current liabilities	(37.9)	(27.7)
Long-term debt, excluding current portion	0.0	0.0
Other long-term liabilities	(599.4)	(565.1)
Intercompany balances	(5,832.2)	(6,112.3)
Stockholders' (deficit) equity	(5,101.6)	(4,988.4)
Total liabilities and stockholders' (deficit) equity	$ (11,571.1)	$ (11,693.5)