Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries - Supplemental Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 118.6	$ 788.8
Restricted cash	33.3	29.0
Accounts receivable, net	562.3	540.9
Notes receivable, net	123.5	143.5
Inventories	231.9	243.1
Prepaid expenses, deposits and other current assets	248.8	131.1
Property and equipment, net	520.2	568.2
Investment in subsidiaries	0.0	0.0
Goodwill	3,312.8	2,956.1
Intangible assets, net	1,797.4	1,604.6
Intercompany balances	0.0	0.0
Software, net	315.8	339.4
Other assets	348.3	380.6
Total assets	7,612.9	7,725.3
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	48.7	40.3
Other current liabilities	638.8	699.5
Long-term debt, excluding current portion	8,845.2	8,736.3
Other long-term liabilities	348.6	276.2
Intercompany balances	0.0	0.0
Stockholders' (deficit) equity	(2,268.4)	(2,027.0)
Total liabilities and stockholders' (deficit) equity	7,612.9	7,725.3
Non-current restricted cash	15.5	16.3
Reportable Legal Entities | SGI (Issuer)
Assets
Cash and cash equivalents	0.0	0.0
Restricted cash	0.6	0.6
Accounts receivable, net	73.9	68.1
Notes receivable, net	0.0	0.0
Inventories	30.7	40.7
Prepaid expenses, deposits and other current assets	66.1	30.3
Property and equipment, net	111.4	91.5
Investment in subsidiaries	929.3	867.9
Goodwill	240.2	240.3
Intangible assets, net	34.5	34.9
Intercompany balances	5,852.9	5,889.8
Software, net	36.1	24.7
Other assets	406.3	388.8
Total assets	7,782.0	7,677.6
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	41.7	32.8
Other current liabilities	123.1	199.0
Long-term debt, excluding current portion	8,844.2	8,733.0
Other long-term liabilities	10.2	11.3
Intercompany balances	0.0	0.0
Stockholders' (deficit) equity	(1,237.2)	(1,298.5)
Total liabilities and stockholders' (deficit) equity	7,782.0	7,677.6
Reportable Legal Entities | SGC (Parent)
Assets
Cash and cash equivalents	44.9	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	11.0	6.5
Property and equipment, net	31.3	28.8
Investment in subsidiaries	3,005.4	3,098.7
Goodwill	0.0	0.0
Intangible assets, net	12.0	15.7
Intercompany balances	0.0	0.0
Software, net	63.2	67.2
Other assets	234.1	234.4
Total assets	3,401.9	4,184.3
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	0.0	0.0
Other current liabilities	99.1	67.6
Long-term debt, excluding current portion	0.0	0.0
Other long-term liabilities	92.2	68.8
Intercompany balances	5,479.0	6,074.9
Stockholders' (deficit) equity	(2,268.4)	(2,027.0)
Total liabilities and stockholders' (deficit) equity	3,401.9	4,184.3
Reportable Legal Entities | Guarantor Subsidiaries
Assets
Cash and cash equivalents	0.0	0.0
Restricted cash	28.0	28.3
Accounts receivable, net	201.9	192.6
Notes receivable, net	107.2	121.1
Inventories	92.0	91.8
Prepaid expenses, deposits and other current assets	98.3	41.6
Property and equipment, net	230.6	295.6
Investment in subsidiaries	1,033.3	987.7
Goodwill	1,886.1	1,880.4
Intangible assets, net	1,245.6	1,335.3
Intercompany balances	0.0	0.0
Software, net	161.0	199.0
Other assets	55.6	62.0
Total assets	5,139.6	5,235.4
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	0.0	0.0
Other current liabilities	219.6	254.2
Long-term debt, excluding current portion	0.0	0.0
Other long-term liabilities	616.7	650.3
Intercompany balances	29.8	37.4
Stockholders' (deficit) equity	4,273.5	4,293.5
Total liabilities and stockholders' (deficit) equity	5,139.6	5,235.4
Non-current restricted cash	14.8	16.1
Reportable Legal Entities | Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents	83.3	59.4
Restricted cash	4.7	0.1
Accounts receivable, net	286.5	279.8
Notes receivable, net	16.3	22.4
Inventories	129.2	131.8
Prepaid expenses, deposits and other current assets	73.2	52.7
Property and equipment, net	174.8	179.9
Investment in subsidiaries	0.0	0.0
Goodwill	1,186.5	835.4
Intangible assets, net	505.3	218.7
Intercompany balances	0.0	222.5
Software, net	55.5	48.5
Other assets	235.4	270.3
Total assets	2,750.7	2,321.5
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	7.0	7.5
Other current liabilities	240.2	206.4
Long-term debt, excluding current portion	1.0	3.3
Other long-term liabilities	198.6	110.9
Intercompany balances	344.1	0.0
Stockholders' (deficit) equity	1,959.8	1,993.4
Total liabilities and stockholders' (deficit) equity	2,750.7	2,321.5
Non-current restricted cash	0.7	0.7
Eliminating Entries
Assets
Cash and cash equivalents	(9.6)	(3.2)
Restricted cash	0.0	0.0
Accounts receivable, net	0.0	0.0
Notes receivable, net	0.0	0.0
Inventories	(20.0)	(21.2)
Prepaid expenses, deposits and other current assets	0.2	0.0
Property and equipment, net	(27.9)	(27.6)
Investment in subsidiaries	(4,968.0)	(4,954.3)
Goodwill	0.0	0.0
Intangible assets, net	0.0	0.0
Intercompany balances	(5,852.9)	(6,112.3)
Software, net	0.0	0.0
Other assets	(583.1)	(574.9)
Total assets	(11,461.3)	(11,693.5)
Liabilities and stockholders' (deficit) equity
Current portion of long-term debt	0.0	0.0
Other current liabilities	(43.2)	(27.7)
Long-term debt, excluding current portion	0.0	0.0
Other long-term liabilities	(569.1)	(565.1)
Intercompany balances	(5,852.9)	(6,112.3)
Stockholders' (deficit) equity	(4,996.1)	(4,988.4)
Total liabilities and stockholders' (deficit) equity	$ (11,461.3)	$ (11,693.5)