Financial Information for Guarantor Subsidiaries and Non-Guarantor Subsidiaries - Supplemental Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 363			$ 168
Restricted cash	46			39
Accounts receivable, net	636			599
Notes receivable, net	123			114
Inventories	257			216
Prepaid expenses, deposits and other current assets	226			233
Property and equipment, net	516			547
Operating lease right-of-use assets	107			0
Investment in subsidiaries	0			0
Goodwill	3,251			3,280
Intangible assets, net	1,579			1,809
Intercompany balances	0			0
Software, net	270			285
Other assets	533			428
Total assets	7,907			7,718
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	288			45
Other current liabilities	757			702
Long-term debt, excluding current portion	8,482			8,992
Operating lease liabilities	91			0
Other long-term liabilities	414			442
Intercompany balances	0			0
Total liabilities and total stockholders’ (deficit) equity	(2,223)		$ (2,423)	(2,463)	$ (2,619)	$ (2,268)	$ (2,196)	$ (2,027)
Stockholders' Equity Attributable to Noncontrolling Interest	98	$ 94		0
Total liabilities and total stockholders’ (deficit) equity	7,907			7,718
Non-current restricted cash	12			13
Reportable Legal Entities | SGI (Issuer)
Assets
Cash and cash equivalents	0			1
Restricted cash	1			1
Accounts receivable, net	105			79
Notes receivable, net	0			0
Inventories	53			40
Prepaid expenses, deposits and other current assets	57			63
Property and equipment, net	95			112
Operating lease right-of-use assets	24
Investment in subsidiaries	992			975
Goodwill	240			240
Intangible assets, net	34			34
Intercompany balances	5,871			6,054
Software, net	36			39
Other assets	436			404
Total assets	7,944			8,042
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	285			42
Other current liabilities	215			162
Long-term debt, excluding current portion	8,474			8,991
Operating lease liabilities	20
Other long-term liabilities	25			8
Intercompany balances	0			0
Total liabilities and total stockholders’ (deficit) equity	(1,075)			(1,161)
Stockholders' Equity Attributable to Noncontrolling Interest	0
Total liabilities and total stockholders’ (deficit) equity	7,944			8,042
Reportable Legal Entities | SGC (Parent)
Assets
Cash and cash equivalents	194			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	6			6
Property and equipment, net	32			31
Operating lease right-of-use assets	1
Investment in subsidiaries	3,147			2,836
Goodwill	0			0
Intangible assets, net	34			43
Intercompany balances	0			0
Software, net	59			58
Other assets	105			110
Total assets	3,578			3,158
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	0			0
Other current liabilities	79			64
Long-term debt, excluding current portion	0			0
Operating lease liabilities	1
Other long-term liabilities	92			106
Intercompany balances	5,629			5,451
Total liabilities and total stockholders’ (deficit) equity	(2,223)			(2,463)
Stockholders' Equity Attributable to Noncontrolling Interest	0
Total liabilities and total stockholders’ (deficit) equity	3,578			3,158
Reportable Legal Entities | Guarantor Subsidiaries
Assets
Cash and cash equivalents	0			0
Restricted cash	37			32
Accounts receivable, net	193			205
Notes receivable, net	110			101
Inventories	114			82
Prepaid expenses, deposits and other current assets	70			92
Property and equipment, net	223			219
Operating lease right-of-use assets	32
Investment in subsidiaries	1,162			1,093
Goodwill	1,897			1,897
Intangible assets, net	1,137			1,291
Intercompany balances	70			0
Software, net	98			128
Other assets	45			46
Total assets	5,188			5,186
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	2			0
Other current liabilities	250			248
Long-term debt, excluding current portion	8			0
Operating lease liabilities	27
Other long-term liabilities	593			637
Intercompany balances	0			49
Total liabilities and total stockholders’ (deficit) equity	4,308			4,252
Stockholders' Equity Attributable to Noncontrolling Interest	0
Total liabilities and total stockholders’ (deficit) equity	5,188			5,186
Non-current restricted cash	11			12
Reportable Legal Entities | Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents	170			94
Restricted cash	8			6
Accounts receivable, net	338			315
Notes receivable, net	13			13
Inventories	103			111
Prepaid expenses, deposits and other current assets	92			72
Property and equipment, net	197			218
Operating lease right-of-use assets	50
Investment in subsidiaries	0			0
Goodwill	1,114			1,143
Intangible assets, net	374			441
Intercompany balances	0			0
Software, net	77			60
Other assets	385			308
Total assets	2,921			2,781
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	1			3
Other current liabilities	246			254
Long-term debt, excluding current portion	0			1
Operating lease liabilities	43
Other long-term liabilities	174			172
Intercompany balances	312			554
Total liabilities and total stockholders’ (deficit) equity	2,047			1,797
Stockholders' Equity Attributable to Noncontrolling Interest	98
Total liabilities and total stockholders’ (deficit) equity	2,921			2,781
Non-current restricted cash	1			1
Eliminating Entries
Assets
Cash and cash equivalents	(1)			(1)
Restricted cash	0			0
Accounts receivable, net	0			0
Notes receivable, net	0			0
Inventories	(13)			(17)
Prepaid expenses, deposits and other current assets	1			0
Property and equipment, net	(31)			(33)
Operating lease right-of-use assets	0
Investment in subsidiaries	(5,301)			(4,904)
Goodwill	0			0
Intangible assets, net	0			0
Intercompany balances	(5,941)			(6,054)
Software, net	0			0
Other assets	(438)			(440)
Total assets	(11,724)			(11,449)
Liabilities and stockholders’ (deficit) equity
Current portion of long-term debt	0			0
Other current liabilities	(33)			(26)
Long-term debt, excluding current portion	0			0
Operating lease liabilities	0
Other long-term liabilities	(470)			(481)
Intercompany balances	(5,941)			(6,054)
Total liabilities and total stockholders’ (deficit) equity	(5,280)			(4,888)
Stockholders' Equity Attributable to Noncontrolling Interest	0
Total liabilities and total stockholders’ (deficit) equity	$ (11,724)			$ (11,449)