Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income from continuing operations	$ 1,826	$ 759
Net income attributable to noncontrolling interests	10	7
Preferred stock dividends	57	63
Preferred stock discount accretion and redemptions	1	1
Net income from continuing operations attributable to common shareholders	1,758	688
Less: Dividends and undistributed earnings allocated to nonvested restricted shares	8	3
Net income from continuing operations attributable to basic common shareholders	1,750	685
Net income from discontinued operations attributable to common shareholders		156
Less: Undistributed earnings allocated to nonvested restricted shares		1
Net income from discontinued operations attributable to basic common shareholders		$ 155
Basic weighted-average common shares outstanding (in shares)	426	429
Basic earnings (loss) per common share from continuing operations (in dollars per share)	$ 4.11	$ 1.59
Basic earnings per common share from discontinued operations (in dollars per share)		0.37
Basic earnings per common share (in dollars per share)	$ 4.11	$ 1.96
Less: Impact of earnings per share dilution from discontinued operations		$ 1
Net income from discontinued operations attributable to diluted common shareholders		$ 154
Dilutive potential common shares (in shares)		1
Diluted weighted-average common shares outstanding (in shares)	426	430
Diluted earnings (loss) per common share from continuing operations (in dollars per share)	$ 4.10	$ 1.59
Diluted earnings per common share from discontinued operations (in dollars per share)		0.36
Diluted earnings per common share (in dollars per share)	$ 4.10	$ 1.95