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)
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 redemption	(247)	$ (247)
Treasury stock purchased (in shares)			(2,000,000)
Treasury stock purchased	(95)					(95)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	13			13
Employee stock purchase plan	11			11
Total comprehensive income (loss):
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 redemption	(247)	$ (247)
Share-based compensation plans	13			13
Employee stock purchase plan	6			6
Total comprehensive income (loss):
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)
Beginning balance (in shares) at Dec. 31, 2021		2,000,000	422,000,000
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	(360)				(360)
Dividends to preferred stockholders	(56)				(56)
Issuance of common stock - business acquisition (in shares)			72,000,000
Issuance of common stock - business acquisition	$ 3,036			3,036
Treasury stock purchased (in shares)	(55,505)
Treasury stock purchased	$ (2)					(2)
Share-based compensation plans (in shares)			2,000,000
Share-based compensation plans	46			46
Employee stock purchase plan	13			13
Total comprehensive income (loss):
Net income	784				784
Other comprehensive income (loss)	(2,553)						(2,553)
Total comprehensive income (loss)	(1,769)				784		(2,553)
Ending balance (in shares) at Jun. 30, 2022		2,000,000	496,000,000
Ending balance at Jun. 30, 2022	24,328	$ 2,014	$ 6	22,100	8,346	(4,920)	(3,218)
Beginning balance (in shares) at Mar. 31, 2022		2,000,000	423,000,000
Beginning balance at Mar. 31, 2022	22,074	$ 2,014	$ 6	19,021	8,209	(4,918)	(2,258)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(195)				(195)
Dividends to preferred stockholders	(32)				(32)
Issuance of common stock - business acquisition (in shares)			72,000,000
Issuance of common stock - business acquisition	3,036			3,036
Treasury stock purchased	(2)					(2)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	36			36
Employee stock purchase plan	7			7
Total comprehensive income (loss):
Net income	364				364
Other comprehensive income (loss)	(960)						(960)
Total comprehensive income (loss)	(596)				364		(960)
Ending balance (in shares) at Jun. 30, 2022		2,000,000	496,000,000
Ending balance at Jun. 30, 2022	$ 24,328	$ 2,014	$ 6	$ 22,100	$ 8,346	$ (4,920)	$ (3,218)