Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries - Supplemental Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 1,213	$ 168
Restricted cash	41	39
Accounts receivable, net	621	599
Notes receivable, net	104	114
Inventories	229	216
Prepaid expenses, deposits and other current assets	238	233
Property and equipment, net	517	547
Operating lease right-of-use assets	118	0
Investment in subsidiaries	0	0
Goodwill	3,301	3,280
Intangible assets, net	1,745	1,809
Intercompany balances	0	0
Software, net	277	285
Other assets	433	428
Total assets	8,837	7,718
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	1,046	45
Other current liabilities	740	702
Long-term debt, excluding current portion	8,937	8,992
Operating lease liabilities	98	0
Other long-term liabilities	439	442
Intercompany balances	0	0
Stockholders’ (deficit) equity	(2,423)	(2,463)	$ (2,196)	$ (2,027)
Total liabilities and stockholders’ (deficit) equity	8,837	7,718
Non-current restricted cash	12	13
Reportable Legal Entities | SGI (Issuer)
Assets
Cash and cash equivalents	1	1
Restricted cash	1	1
Accounts receivable, net	102	79
Notes receivable, net	0	0
Inventories	45	40
Prepaid expenses, deposits and other current assets	60	63
Property and equipment, net	99	112
Operating lease right-of-use assets	24
Investment in subsidiaries	959	975
Goodwill	240	240
Intangible assets, net	34	34
Intercompany balances	7,096	6,054
Software, net	37	39
Other assets	412	404
Total assets	9,110	8,042
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	1,042	42
Other current liabilities	224	162
Long-term debt, excluding current portion	8,928	8,991
Operating lease liabilities	20
Other long-term liabilities	13	8
Intercompany balances	0	0
Stockholders’ (deficit) equity	(1,117)	(1,161)
Total liabilities and stockholders’ (deficit) equity	9,110	8,042
Reportable Legal Entities | SGC (Parent)
Assets
Cash and cash equivalents	1,119	74
Restricted cash	0	0
Accounts receivable, net	0	0
Notes receivable, net	0	0
Inventories	0	0
Prepaid expenses, deposits and other current assets	3	6
Property and equipment, net	31	31
Operating lease right-of-use assets	1
Investment in subsidiaries	2,896	2,836
Goodwill	0	0
Intangible assets, net	40	43
Intercompany balances	0	0
Software, net	53	58
Other assets	113	110
Total assets	4,256	3,158
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	0	0
Other current liabilities	58	64
Long-term debt, excluding current portion	0	0
Operating lease liabilities	1
Other long-term liabilities	104	106
Intercompany balances	6,516	5,451
Stockholders’ (deficit) equity	(2,423)	(2,463)
Total liabilities and stockholders’ (deficit) equity	4,256	3,158
Reportable Legal Entities | Guarantor Subsidiaries
Assets
Cash and cash equivalents	0	0
Restricted cash	33	32
Accounts receivable, net	204	205
Notes receivable, net	89	101
Inventories	89	82
Prepaid expenses, deposits and other current assets	95	92
Property and equipment, net	208	219
Operating lease right-of-use assets	35
Investment in subsidiaries	1,216	1,093
Goodwill	1,897	1,897
Intangible assets, net	1,239	1,291
Intercompany balances	74	0
Software, net	118	128
Other assets	37	46
Total assets	5,334	5,186
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	3	0
Other current liabilities	235	248
Long-term debt, excluding current portion	8	0
Operating lease liabilities	30
Other long-term liabilities	637	637
Intercompany balances	0	49
Stockholders’ (deficit) equity	4,421	4,252
Total liabilities and stockholders’ (deficit) equity	5,334	5,186
Non-current restricted cash	11	12
Reportable Legal Entities | Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents	95	94
Restricted cash	7	6
Accounts receivable, net	315	315
Notes receivable, net	15	13
Inventories	109	111
Prepaid expenses, deposits and other current assets	79	72
Property and equipment, net	215	218
Operating lease right-of-use assets	58
Investment in subsidiaries	0	0
Goodwill	1,164	1,143
Intangible assets, net	432	441
Intercompany balances	0	0
Software, net	69	60
Other assets	309	308
Total assets	2,867	2,781
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	1	3
Other current liabilities	258	254
Long-term debt, excluding current portion	1	1
Operating lease liabilities	47
Other long-term liabilities	176	172
Intercompany balances	654	554
Stockholders’ (deficit) equity	1,730	1,797
Total liabilities and stockholders’ (deficit) equity	2,867	2,781
Non-current restricted cash	1	1
Eliminating Entries
Assets
Cash and cash equivalents	(2)	(1)
Restricted cash	0	0
Accounts receivable, net	0	0
Notes receivable, net	0	0
Inventories	(14)	(17)
Prepaid expenses, deposits and other current assets	1	0
Property and equipment, net	(36)	(33)
Operating lease right-of-use assets	0
Investment in subsidiaries	(5,071)	(4,904)
Goodwill	0	0
Intangible assets, net	0	0
Intercompany balances	(7,170)	(6,054)
Software, net	0	0
Other assets	(438)	(440)
Total assets	(12,730)	(11,449)
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	0	0
Other current liabilities	(35)	(26)
Long-term debt, excluding current portion	0	0
Operating lease liabilities	0
Other long-term liabilities	(491)	(481)
Intercompany balances	(7,170)	(6,054)
Stockholders’ (deficit) equity	(5,034)	(4,888)
Total liabilities and stockholders’ (deficit) equity	$ (12,730)	$ (11,449)