(Loss) Income Per Common Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator (basic and diluted):
(Loss) income from continuing operations	$ (36)		$ 210	$ 58	$ 343
Less: Allocation to redeemable noncontrolling interest	0	$ 6	0	6	0
Less: Allocation to unvested restricted stock awards	0		2	0	3
(Loss) income from continuing operations attributable to common shareholders	(36)		208	52	340
Income from discontinued operations, net	0		14	0	411
Less: Allocation to unvested restricted stock awards	0		0	0	3
Income from discontinued operations, net attributable to common shareholders	0		14	0	408
Net (loss) income attributable to common shareholders	$ (36)		$ 222	$ 52	$ 748
Denominator:
Basic common shares (based upon weighted average) (in shares)	252		262	254	267
Add: Stock option dilution (in shares)	0		1	2	1
Diluted common shares (in shares)	252		263	256	268