Earnings per Common Share (Schedule of Basic and Diluted Earnings per Common Share) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income (loss) from continuing operations		$ 899	$ 242	$ 1,695	$ (77)
Income (loss) from discontinued operations, net of tax		1	(1)	1	(1)
Net income (loss)		$ 900	$ 241	$ 1,696	$ (78)
Basic weighted-average common shares outstanding		370,412,000	375,051,000	372,807,000	375,387,000
Diluted weighted-average common shares outstanding		373,029,000	375,762,000	375,265,000	375,387,000
Basic earnings per common share
Net income (loss) from continuing operations (in dollars per share)	[1]	$ 2.43	$ 0.65	$ 4.55	$ (0.20)
Net income (loss) (in dollars per share)	[1]	2.43	0.64	4.55	(0.21)
Diluted earnings per common share
Net income (loss) from continuing operations (in dollars per share)	[1],[2]	2.41	0.64	4.52	(0.20)
Net income (loss) (in dollars per share)	[1],[2]	$ 2.41	$ 0.64	$ 4.52	$ (0.21)
Antidilutive securities excluded from computation of earnings per share, amount		0	2,300,000	0	2,400,000

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

[2] Due to the antidilutive effect of the net loss from continuing operations for the six months ended June 30, 2020, basic weighted-average common shares outstanding was used to calculate basic and diluted earnings per share.