Parent Company Financial Statements - Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating Activities:
Net cash provided by (used in) operating activities	$ (13,210)	$ 690	$ 11,954
Investing Activities:
Net increase (decrease) in interest-bearing deposits with consolidated banking subsidiary	(25,292)	13,928	4,765
Purchases of available-for-sale securities	(44,301)	(23,089)	(18,029)
Net cash (used in) provided by investing activities	(39,483)	12,738	6,816
Financing Activities:
Proceeds from issuance of long-term debt, net of issuance costs	6,523	6,221	3,731
Payments for long-term debt	(2,046)	(2,545)	(1,567)
Proceeds from issuance of preferred stock, net of issuance costs	2,323	0	0
Payments for redemption of preferred stock	(1,500)	0	0
Repurchases of common stock	(1,319)	(3,781)	(1,500)
Repurchases of common stock for employee tax withholding	(83)	(95)	(123)
Payments for cash dividends	(1,033)	(970)	(972)
Net cash provided by (used in) financing activities	51,791	(13,351)	(18,431)
Net (decrease) increase	(902)	77	339
Cash and due from banks at beginning of period	4,047	3,970	3,631
Cash and due from banks at end of period	3,145	4,047	3,970
Parent Company
Operating Activities:
Net cash provided by (used in) operating activities	622	4,194	1,608
Investing Activities:
Net increase (decrease) in interest-bearing deposits with consolidated banking subsidiary	221	(199)	22
Proceeds from sales and maturities of available-for-sale securities	1,120	830	780
Purchases of available-for-sale securities	(1,204)	(836)	(886)
Investments in consolidated banking and non-banking subsidiaries	(9,330)	(10,784)	(16,252)
Sale or repayment of investment in consolidated banking and non-banking subsidiaries	7,875	7,920	15,092
Net cash (used in) provided by investing activities	(1,318)	(3,069)	(1,244)
Financing Activities:
Proceeds from issuance of long-term debt, net of issuance costs	4,281	6,221	3,731
Payments for long-term debt	(2,000)	(2,500)	(1,500)
Proceeds from issuance of preferred stock, net of issuance costs	2,350	0	0
Payments for redemption of preferred stock	(1,500)	0	0
Repurchases of common stock	(1,319)	(3,781)	(1,500)
Repurchases of common stock for employee tax withholding	(83)	(95)	(123)
Payments for cash dividends	(1,033)	(970)	(972)
Net cash provided by (used in) financing activities	696	(1,125)	(364)
Net (decrease) 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