CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (unaudited) - USD ($) $ in Millions	Total	Series H Preferred Stock	Series I Preferred Stock	Series J Preferred Stock	Series K Preferred Stock	Series L Preferred Stock	Class B, Series A 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 H Preferred Stock	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 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	823															823
Other comprehensive income (loss), net of tax	1,639																								1,639
Cash dividends declared:
Common stock	(585)															(585)
Preferred stock		$ (15)	$ (23)	$ (10)	$ (9)	$ (3)	$ (9)										$ (15)	$ (23)	$ (10)	$ (9)	$ (3)	$ (9)
Issuance of preferred stock	346											346
Impact of stock transactions under stock compensation plans, net	66													25													41
Other	0															(2)											2
Ending Balance at Sep. 30, 2020	22,951									2,051		2,116		3,624		18,010									2,831		(5,681)
Beginning Balance at Jun. 30, 2020	22,335									2,051		1,770		3,603		17,643									2,951		(5,683)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	581															581
Other comprehensive income (loss), net of tax	(120)																								(120)
Cash dividends declared:
Common stock	(195)															(195)
Preferred stock			(7)	(3)	(3)	(3)	(3)											(7)	(3)	(3)	(3)	(3)
Issuance of preferred stock	346											346
Impact of stock transactions under stock compensation plans, net	23													21													2
Ending Balance at Sep. 30, 2020	22,951									2,051		2,116		3,624		18,010									2,831		(5,681)
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	2,107															2,107
Other comprehensive income (loss), net of tax	(964)																								(964)
Cash dividends declared:
Common stock	(597)															(597)
Preferred stock		$ (15)	(22)	(8)	(9)	(12)	(9)										$ (15)	(22)	(8)	(9)	(12)	(9)
Shares acquired for treasury	(1,077)																										(1,077)
Impact of stock transactions under stock compensation plans, net	20													(24)													44
Other	(1)															(2)											1
Ending Balance at Sep. 30, 2021	22,524									2,051		2,116		3,611		19,817									1,637		(6,708)
Beginning Balance at Jun. 30, 2021	22,926									2,051		2,116		3,602		19,343									1,974		(6,160)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	704															704
Other comprehensive income (loss), net of tax	(337)																								(337)
Cash dividends declared:
Common stock	(210)															(210)
Preferred stock			$ (7)	$ (3)	$ (3)	$ (4)	$ (3)											$ (7)	$ (3)	$ (3)	$ (4)	$ (3)
Shares acquired for treasury	(550)																										(550)
Impact of stock transactions under stock compensation plans, net	11													9													2
Ending Balance at Sep. 30, 2021	$ 22,524									$ 2,051		$ 2,116		$ 3,611		$ 19,817									$ 1,637		$ (6,708)