Earnings per Common Share (Schedule of Basic and Diluted Earnings per Common Share) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Class of Stock [Line Items]
Net income from continuing operations attributable to common stockholders	[1]	$ 712	$ 476	$ 2,407	$ 399
Net income from continuing operations attributable to common stockholders	[1]	683	476	2,378	399
Income (loss) from discontinued operations, net of tax	[1]	0	0	1	(1)
Net income attributable to common stockholders	[1]	$ 683	$ 476	$ 2,379	$ 398
Basic weighted-average common shares outstanding	[1],[2]	359,179,000	375,658,000	368,215,000	375,478,000
Diluted weighted-average common shares outstanding	[1],[2],[3]	361,855,000	377,011,000	370,745,000	376,659,000
Basic earnings per common share
Net income (loss) from continuing operations (in dollars per share)	[1]	$ 1.90	$ 1.27	$ 6.46	$ 1.06
Net income (loss) (in dollars per share)	[1]	1.90	1.27	6.46	1.06
Diluted earnings per common share
Net income (loss) from continuing operations (in dollars per share)	[1]	1.89	1.26	6.41	1.06
Net income (loss) (in dollars per share)	[1]	$ 1.89	$ 1.26	$ 6.42	$ 1.06
Antidilutive securities excluded from computation of earnings per share, amount		0	400,000	0	1,000,000
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends	[1]	$ (20)	$ 0	$ (20)	$ 0
Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends	[1]	$ (9)	$ 0	$ (9)	$ 0

[1] Figures in the table may not recalculate exactly due to rounding. Earnings per share is calculated based on unrounded numbers.

[2] Includes shares related to share-based compensation that vested but were not yet issued.

[3] During the three months and nine months ended September 30, 2020, there were 0.4 million and 1.0 million, respectively, in shares underlying share-based awards excluded because their inclusion would have been antidilutive. There were no antidilutive shares during the three months and nine months ended September 30, 2021.