Parent Company Financial Statements - Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities:
Net cash (used in) provided by operating activities	$ (6,710)	$ 3,532	$ 5,690
Investing Activities:
Net decrease (increase) in interest-bearing deposits with consolidated banking subsidiary	10,602	(47,995)	4,075
Purchases of available-for-sale securities	(53,750)	(37,873)	(38,164)
Net cash provided by (used in) investing activities	(2,172)	(65,534)	(2,626)
Financing Activities:
Proceeds from issuance of long-term debt, net of issuance costs	1,343	2,489	1,495
Payments for long-term debt	(1,443)	(1,724)	(402)
Payments for redemption of preferred stock	(500)	(500)	(750)
Proceeds from issuance of common stock, net of issuance costs	1,900	0	0
Repurchases of common stock	(900)	(515)	(1,585)
Repurchases of common stock for employee tax withholding	(39)	(78)	(81)
Payments for cash dividends	(866)	(889)	(930)
Net cash provided by (used in) financing activities	9,046	62,167	(2,974)
Net increase	164	165	90
Cash and due from banks at beginning of period	3,467	3,302	3,212
Cash and due from banks at end of period	3,631	3,467	3,302
Parent Company
Operating Activities:
Net cash (used in) provided by operating activities	(116)	3,513	2,684
Investing Activities:
Net decrease (increase) in interest-bearing deposits with consolidated banking subsidiary	10	(64)	58
Proceeds from sales and maturities of available-for-sale securities	525	1,000	900
Purchases of available-for-sale securities	(575)	(849)	(921)
Investments in consolidated banking and non-banking subsidiaries	(6,288)	(7,406)	(6,165)
Sale or repayment of investment in consolidated banking and non-banking subsidiaries	7,006	4,999	5,345
Net cash provided by (used in) investing activities	678	(2,320)	(783)
Financing Activities:
Proceeds from issuance of long-term debt, net of issuance costs	1,343	2,489	1,495
Payments for long-term debt	(1,500)	(1,700)	(50)
Payments for redemption of preferred stock	(500)	(500)	(750)
Proceeds from issuance of common stock, net of issuance costs	1,900	0	0
Repurchases of common stock	(900)	(515)	(1,585)
Repurchases of common stock for employee tax withholding	(39)	(78)	(81)
Payments for cash dividends	(866)	(889)	(930)
Net cash provided by (used in) financing activities	(562)	(1,193)	(1,901)
Net increase	0	0	0
Cash and due from banks at beginning of period	0	0	0
Cash and due from banks at end of period	$ 0	$ 0	$ 0