Parent Company Financial Statements - Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Activities:
Net cash provided by (used in) operating activities	$ 690	$ 11,954	$ (6,710)
Investing Activities:
Net (increase) decrease in interest-bearing deposits with consolidated banking subsidiary	13,928	4,765	10,602
Purchases of available-for-sale securities	(23,089)	(18,029)	(53,750)
Net cash provided by (used in) investing activities	12,738	6,816	(2,172)
Financing Activities:
Proceeds from issuance of long-term debt, net of issuance costs	6,221	3,731	1,343
Payments for long-term debt	(2,545)	(1,567)	(1,443)
Payments for redemption of preferred stock	0	0	(500)
Proceeds from issuance of common stock, net of issuance costs	0	0	1,900
Repurchases of common stock	(3,781)	(1,500)	(900)
Repurchases of common stock for employee tax withholding	(95)	(123)	(39)
Payments for cash dividends	(970)	(972)	(866)
Net cash (used in) provided by financing activities	(13,351)	(18,431)	9,046
Net increase	77	339	164
Cash and due from banks at beginning of period	3,970	3,631	3,467
Cash and due from banks at end of period	4,047	3,970	3,631
Parent Company
Operating Activities:
Net cash provided by (used in) operating activities	4,194	1,608	(116)
Investing Activities:
Net (increase) decrease in interest-bearing deposits with consolidated banking subsidiary	(199)	22	10
Proceeds from sales and maturities of available-for-sale securities	830	780	525
Purchases of available-for-sale securities	(836)	(886)	(575)
Investments in consolidated banking and non-banking subsidiaries	(10,784)	(16,252)	(6,288)
Sale or repayment of investment in consolidated banking and non-banking subsidiaries	7,920	15,092	7,006
Net cash provided by (used in) investing activities	(3,069)	(1,244)	678
Financing Activities:
Proceeds from issuance of long-term debt, net of issuance costs	6,221	3,731	1,343
Payments for long-term debt	(2,500)	(1,500)	(1,500)
Payments for redemption of preferred stock	0	0	(500)
Proceeds from issuance of common stock, net of issuance costs	0	0	1,900
Repurchases of common stock	(3,781)	(1,500)	(900)
Repurchases of common stock for employee tax withholding	(95)	(123)	(39)
Payments for cash dividends	(970)	(972)	(866)
Net cash (used in) provided by financing activities	(1,125)	(364)	(562)
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