Stockholders' Deficit - Schedule of Changes in Equity (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total SGC stockholders' deficit		$ (2,653)	$ (2,358)	$ (2,108)	$ (2,653)	$ (2,108)
Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance		129			129
Vesting of RSUs, net of tax withholdings and other	$ (4)	(13)	1	(1)
Stock-based compensation	31	17	14	9
Net income (loss)	113	(9)	(198)	(155)	104	(353)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	11	8	62	(97)	19	$ (35)
Accounting Standards Update [Extensible List]						us-gaap:AccountingStandardsUpdate201905Member
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(2,370)	(2,521)			(2,370)		$ (2,524)
Less: comprehensive income attributable to noncontrolling interest	4		5		10	$ 9
Stockholders' Equity Attributable to Noncontrolling Interest	139				139
Total SGC stockholders' deficit	(2,509)		(2,479)	(2,358)	(2,509)	(2,479)
Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest				(6)
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total SGC stockholders' deficit			1	1		1
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1	1			1		1
Total SGC stockholders' deficit			1	1		1
Additional Paid in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total SGC stockholders' deficit			1,216	1,208		1,208
Vesting of RSUs, net of tax withholdings and other	(4)	(13)	1	(1)
Stock-based compensation	31	17	13	9
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,299	1,272			1,299		1,268
Total SGC stockholders' deficit			1,230	1,216		1,230
Accumulated Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total SGC stockholders' deficit			(3,119)	(2,954)		(2,954)
Net income (loss)	109	(15)	(203)	(159)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(3,435)	(3,544)			(3,435)		(3,529)
Total SGC stockholders' deficit			(3,322)	(3,119)		(3,322)
Accumulated Loss | Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total SGC stockholders' deficit				6		6
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest				(6)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total SGC stockholders' deficit			(175)	(175)		(175)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(175)	(175)			(175)		(175)
Total SGC stockholders' deficit			(175)	(175)		(175)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total SGC stockholders' deficit			(389)	(292)		(292)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		8	62	(97)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(199)	(210)			(199)		$ (218)
Total SGC stockholders' deficit			(327)	(389)		(327)
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance	$ 135	129	108	104	$ 129	104
Stock-based compensation			1
Net income (loss)			5	4
Less: comprehensive income attributable to noncontrolling interest		6
Stockholders' Equity Attributable to Noncontrolling Interest		$ 135	$ 114	$ 108		$ 114