CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) shares in Millions, $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock, at Cost	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2020		2	427
Beginning balance at Dec. 31, 2020	$ 22,673	$ 1,965	$ 6	$ 18,940	$ 6,445	$ (4,623)	$ (60)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(167)				(167)
Dividends to preferred stockholders	(23)				(23)
Treasury stock purchased (in shares)			(2)
Treasury stock purchased	(95)					(95)
Share-based compensation plans (in shares)			1
Employee stock purchase plan	5			5
Total comprehensive income:
Net income	611				611
Other comprehensive income (loss)	(351)						(351)
Total comprehensive income (loss)	260				611		(351)
Ending balance (in shares) at Mar. 31, 2021		2	426
Ending balance at Mar. 31, 2021	22,653	$ 1,965	$ 6	18,945	6,866	(4,718)	(411)
Beginning balance (in shares) at Dec. 31, 2021		2	422
Beginning balance at Dec. 31, 2021	23,420	$ 2,014	$ 6	19,005	7,978	(4,918)	(665)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(165)				(165)
Dividends to preferred stockholders	(24)				(24)
Share-based compensation plans (in shares)			1
Share-based compensation plans	10			10
Employee stock purchase plan	6			6
Total comprehensive income:
Net income	420				420
Other comprehensive income (loss)	(1,593)						(1,593)
Total comprehensive income (loss)	(1,173)				420		(1,593)
Ending balance (in shares) at Mar. 31, 2022		2	423
Ending balance at Mar. 31, 2022	$ 22,074	$ 2,014	$ 6	$ 19,021	$ 8,209	$ (4,918)	$ (2,258)