CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock, at Cost	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect, Period Of Adoption, Adjustment	Cumulative Effect, Period Of Adoption, Adjustment Retained Earnings
Beginning balance (in shares) at Dec. 31, 2019		2,000,000	433,000,000
Beginning balance at Dec. 31, 2019	$ 22,201	$ 1,570	$ 6	$ 18,891	$ 6,498	$ (4,353)	$ (411)	$ (331)	$ (331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(336)				(336)
Dividends to preferred stockholders	(50)				(50)
Preferred stock issued	395	$ 395
Treasury stock purchased (in shares)			(7,000,000)
Treasury stock purchased	(270)					(270)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	7			7		0
Employee stock purchase plan purchased	10			10
Total comprehensive income:
Net income	287				287
Other comprehensive income (loss)	505						505
Total comprehensive income (loss)	792				287		505
Ending balance (in shares) at Jun. 30, 2020		2,000,000	427,000,000
Ending balance at Jun. 30, 2020	22,418	$ 1,965	$ 6	18,908	6,068	(4,623)	94
Beginning balance (in shares) at Mar. 31, 2020		2,000,000	427,000,000
Beginning balance at Mar. 31, 2020	21,950	$ 1,570	$ 6	18,901	6,011	(4,623)	85
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(168)				(168)
Dividends to preferred stockholders	(28)				(28)
Preferred stock issued	395	$ 395
Treasury stock purchased	0
Share-based compensation plans	1			1
Employee stock purchase plan purchased	6			6
Total comprehensive income:
Net income	253				253
Other comprehensive income (loss)	9						9
Total comprehensive income (loss)	262				253		9
Ending balance (in shares) at Jun. 30, 2020		2,000,000	427,000,000
Ending balance at Jun. 30, 2020	22,418	$ 1,965	$ 6	18,908	6,068	(4,623)	94
Beginning balance (in shares) at Dec. 31, 2020		2,000,000	427,000,000
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	(335)				(335)
Dividends to preferred stockholders	(55)				(55)
Preferred stock issued	296	296
Preferred stock called	$ (247)	$ (247)
Treasury stock purchased (in shares)	(2,244,924)		(2,000,000)
Treasury stock purchased	$ (95)					(95)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	13			13		0
Employee stock purchase plan purchased	11			11
Total comprehensive income:
Net income	1,259				1,259
Other comprehensive income (loss)	(321)						(321)
Total comprehensive income (loss)	938				1,259		(321)
Ending balance (in shares) at Jun. 30, 2021		2,000,000	426,000,000
Ending balance at Jun. 30, 2021	23,199	$ 2,014	$ 6	18,964	7,314	(4,718)	(381)
Beginning balance (in shares) at Mar. 31, 2021		2,000,000	426,000,000
Beginning balance at Mar. 31, 2021	22,653	$ 1,965	$ 6	18,945	6,866	(4,718)	(411)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(168)				(168)
Dividends to preferred stockholders	(32)				(32)
Preferred stock issued	296	296
Preferred stock called	(247)	$ (247)
Share-based compensation plans	13			13
Employee stock purchase plan purchased	6			6
Total comprehensive income:
Net income	648				648
Other comprehensive income (loss)	30						30
Total comprehensive income (loss)	678				648		30
Ending balance (in shares) at Jun. 30, 2021		2,000,000	426,000,000
Ending balance at Jun. 30, 2021	$ 23,199	$ 2,014	$ 6	$ 18,964	$ 7,314	$ (4,718)	$ (381)