CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (unaudited) - USD ($) $ in Millions	Total	Series I Preferred Stock	Series J Preferred Stock	Series K Preferred Stock	Series L Preferred Stock	Class B, Series A Preferred Stock	Series H Preferred Stock	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Preferred Stock	Preferred Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Capital Surplus	Capital Surplus Cumulative Effect, Period of Adoption, Adjusted Balance	Retained Earnings	Retained Earnings Series I Preferred Stock	Retained Earnings Series J Preferred Stock	Retained Earnings Series K Preferred Stock	Retained Earnings Series L Preferred Stock	Retained Earnings Class B, Series A Preferred Stock	Retained Earnings Series H Preferred Stock	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Other Comprehensive Income	Accumulated Other Comprehensive Income Cumulative Effect, Period of Adoption, Adjusted Balance	Treasury Stock	Treasury Stock Cumulative Effect, Period of Adoption, Adjusted Balance
Beginning Balance at Dec. 31, 2019	$ 21,203							$ (472)	$ 20,731	$ 2,051	$ 2,051	$ 1,770	$ 1,770	$ 3,599	$ 3,599	$ 18,315							$ (472)	$ 17,843	$ 1,192	$ 1,192	$ (5,724)	$ (5,724)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	243															243
Other comprehensive income (loss), net of tax	1,759																								1,759
Cash dividends declared:
Common stock	(390)															(390)
Preferred stock		$ (15)	$ (8)	$ (6)		$ (6)	$ (15)										$ (15)	$ (8)	$ (6)		$ (6)	$ (15)
Impact of stock transactions under stock compensation plans, net	43													4													39
Other	(1)															(3)											2
Ending Balance at Jun. 30, 2020	22,335									2,051		1,770		3,603		17,643									2,951		(5,683)
Beginning Balance at Mar. 31, 2020	21,873									2,051		1,770		3,597		17,677									2,477		(5,699)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	195															195
Other comprehensive income (loss), net of tax	474																								474
Cash dividends declared:
Common stock	(195)															(195)
Preferred stock		(7)	(4)	(3)		(3)	(15)										(7)	(4)	(3)		(3)	(15)
Impact of stock transactions under stock compensation plans, net	20													6													14
Other	0															(2)											2
Ending Balance at Jun. 30, 2020	22,335									2,051		1,770		3,603		17,643									2,951		(5,683)
Beginning Balance at Dec. 31, 2020	23,111									2,051		2,116		3,635		18,384									2,601		(5,676)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,403															1,403
Other comprehensive income (loss), net of tax	(627)																								(627)
Cash dividends declared:
Common stock	(387)															(387)
Preferred stock		(15)	(5)	(6)	$ (8)	(6)	(15)										(15)	(5)	(6)	$ (8)	(6)	(15)
Shares acquired for treasury	(527)																										(527)
Impact of stock transactions under stock compensation plans, net	9													(33)													42
Other	(1)															(2)											1
Ending Balance at Jun. 30, 2021	22,926									2,051		2,116		3,602		19,343									1,974		(6,160)
Beginning Balance at Mar. 31, 2021	22,595									2,051		2,116		3,592		18,863									1,792		(5,819)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	709															709
Other comprehensive income (loss), net of tax	182																								182
Cash dividends declared:
Common stock	(192)															(192)
Preferred stock		$ (7)	$ (3)	$ (3)	$ (4)	$ (3)	$ (15)										$ (7)	$ (3)	$ (3)	$ (4)	$ (3)	$ (15)
Shares acquired for treasury	(347)																										(347)
Impact of stock transactions under stock compensation plans, net	15													10													5
Other	(1)															(2)											1
Ending Balance at Jun. 30, 2021	$ 22,926									$ 2,051		$ 2,116		$ 3,602		$ 19,343									$ 1,974		$ (6,160)