Income Per Common Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator (basic and diluted):
Income from continuing operations	$ 220		$ 275	$ 278	$ 618
Less: Allocation to redeemable noncontrolling interest	0	$ 6	0	6	0
Less: Allocation to unvested restricted stock awards	1		1	1	5
Income from continuing operations attributable to common shareholders	219		274	271	613
Income from discontinued operations, net	0		0	0	411
Less: Allocation to unvested restricted stock awards	0		0	0	3
Income from discontinued operations, net attributable to common shareholders	0		0	0	408
Net income attributable to common shareholders	$ 219		$ 274	$ 271	$ 1,021
Denominator:
Basic common shares (based upon weighted average) (in shares)	246		261	251	265
Add: Stock option dilution (in shares)	1		0	2	1
Diluted common shares (in shares)	247		261	253	266