Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income from continuing operations	$ 1,490	$ 1,532	$ 4,419	$ 1,547
Net income attributable to noncontrolling interests	16	13	38	27
Preferred stock dividends	57	63	162	181
Preferred stock discount accretion and redemptions	1	1	3	3
Net income from continuing operations attributable to common shareholders	1,416	1,455	4,216	1,336
Less: Dividends and undistributed earnings allocated to nonvested restricted shares	8	8	21	7
Net income from continuing operations attributable to basic common shareholders	1,408	1,447	4,195	1,329
Net income from discontinued operations attributable to common shareholders				4,555
Less: Undistributed earnings allocated to nonvested restricted shares				22
Net income from discontinued operations attributable to basic common shareholders				$ 4,533
Basic weighted-average common shares outstanding (in shares)	426	426	426	427
Basic earnings from continuing operations (in dollars per share)	$ 3.31	$ 3.40	$ 9.84	$ 3.11
Basic earnings per common share from discontinued operations (in dollars per share)				10.61
Basic earnings per common share (in dollars per share)	$ 3.31	$ 3.40	$ 9.84	$ 13.73
Net income from continuing operations attributable to diluted common shareholders	$ 1,408	$ 1,447	$ 4,195	$ 1,329
Less: Impact of earnings per share dilution from discontinued operations				2
Net income from discontinued operations attributable to diluted common shareholders				$ 4,531
Dilutive potential common shares (in shares)			1	1
Diluted weighted-average common shares outstanding (in shares)	426	426	427	428
Diluted earnings from continuing operations (in dollars per share)	$ 3.30	$ 3.39	$ 9.83	$ 3.11
Diluted earnings per common share from discontinued operations (in dollars per share)				10.59
Diluted earnings per common share (in dollars per share)	$ 3.30	$ 3.39	$ 9.83	$ 13.70