CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock, at Cost	Accumulated Other Comprehensive Income (Loss)
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	(569)					(569)
Dividends to preferred stockholders	(81)					(81)
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)				2,000,000
Share-based compensation plans	61				61
Employee stock purchase plan	19				19
Total comprehensive income (loss):
Net income	1,420					1,420
Other comprehensive income (loss)	(4,158)								(4,158)
Total comprehensive income (loss)	(2,738)					1,420			(4,158)
Ending balance (in shares) at Sep. 30, 2022			2,000,000	496,000,000
Ending balance at Sep. 30, 2022	23,146		$ 2,014	$ 6	22,121	8,748		(4,920)	(4,823)
Beginning balance (in shares) at Jun. 30, 2022			2,000,000	496,000,000
Beginning balance at Jun. 30, 2022	24,328		$ 2,014	$ 6	22,100	8,346		(4,920)	(3,218)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(209)					(209)
Dividends to preferred stockholders	(25)					(25)
Share-based compensation plans	15				15
Employee stock purchase plan	6				6
Total comprehensive income (loss):
Net income	636					636
Other comprehensive income (loss)	(1,605)								(1,605)
Total comprehensive income (loss)	(969)					636			(1,605)
Ending balance (in shares) at Sep. 30, 2022			2,000,000	496,000,000
Ending balance at Sep. 30, 2022	23,146		$ 2,014	$ 6	22,121	8,748		(4,920)	(4,823)
Beginning balance (in shares) at Dec. 31, 2022			2,000,000	492,000,000
Beginning balance at Dec. 31, 2022	23,690	$ (26)	$ 2,014	$ 6	22,142	9,159	$ (26)	(5,071)	(4,560)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(609)					(609)
Dividends to preferred stockholders	$ (87)					(87)
Treasury stock purchased (in shares)	(28,472,450)			(29,000,000)
Treasury stock purchased	$ (906)							(906)
Share repurchase excise tax	(9)							(9)
Share-based compensation plans (in shares)				3,000,000
Share-based compensation plans	68				68
Employee stock purchase plan	21				21
Total comprehensive income (loss):
Net income	1,419					1,419
Other comprehensive income (loss)	(683)								(683)
Total comprehensive income (loss)	736					1,419			(683)
Ending balance (in shares) at Sep. 30, 2023			2,000,000	466,000,000
Ending balance at Sep. 30, 2023	22,878		$ 2,014	$ 6	22,231	9,856		(5,986)	(5,243)
Beginning balance (in shares) at Jun. 30, 2023			2,000,000	475,000,000
Beginning balance at Jun. 30, 2023	23,585		$ 2,014	$ 6	22,207	9,655		(5,734)	(4,563)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(199)					(199)
Dividends to preferred stockholders	(30)					(30)
Treasury stock purchased (in shares)				(9,000,000)
Treasury stock purchased	(250)							(250)
Share repurchase excise tax	(2)							(2)
Share-based compensation plans	17				17
Employee stock purchase plan	7				7
Total comprehensive income (loss):
Net income	430					430
Other comprehensive income (loss)	(680)								(680)
Total comprehensive income (loss)	(250)					430			(680)
Ending balance (in shares) at Sep. 30, 2023			2,000,000	466,000,000
Ending balance at Sep. 30, 2023	$ 22,878		$ 2,014	$ 6	$ 22,231	$ 9,856		$ (5,986)	$ (5,243)