Parent Company Financial Information - Parent Company Condensed Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows From Operating Activities:
Net income	$ 6,437	$ 4,492	$ 3,237
Adjustments to reconcile net income to net cash from operating activities:
Other, net	229	(499)	100
Net cash from operating activities	7,892	7,437	1,520
Cash Flows From Investing Activities:
Proceeds from maturities, calls and paydowns of AFS securities	33,968	24,627	4,797
Purchases of AFS securities	(70,775)	(72,808)	(42,646)
Proceeds from maturities, calls and paydowns of HTM securities	0	0	2,499
Net cash from acquisitions and divestitures	1,638	2,439	(6,256)
Other, net	(331)	(461)	108
Net cash from investing activities	(32,056)	(43,652)	8,348
Cash Flows From Financing Activities:
Proceeds from (Repayments of) Other Debt	(800)	(12,124)	6,293
Repurchase of common stock	(1,616)	0	0
Proceeds from Issuance of Preferred Stock and Preference Stock	0	3,449	1,683
Redemption of preferred stock	(1,415)	(500)	(1,725)
Other, net	82	(148)	(45)
Net Cash Provided by (Used in) Financing Activities	25,591	36,018	5,353
Cash and Cash Equivalents, at Carrying Value	20,295	18,868	19,065	$ 3,844
Parent Company
Cash Flows From Operating Activities:
Net income	6,437	4,492	3,237
Adjustments to reconcile net income to net cash from operating activities:
Equity in earnings of subsidiaries in excess of dividends from subsidiaries	(2,427)	(1,956)	(1,968)
Other, net	(438)	(704)	84
Net cash from operating activities	3,572	1,832	1,353
Cash Flows From Investing Activities:
Proceeds from maturities, calls and paydowns of AFS securities	37	79	157
Purchases of AFS securities	(216)	(22)	(79)
Investment in subsidiaries	(120)	(79)	(1)
Advances to subsidiaries	(3,088)	(6,711)	(5,358)
Proceeds from repayment of advances to subsidiaries	3,922	5,499	8,304
Net cash from acquisitions and divestitures	0	0	(1,903)
Other, net	0	14	(1)
Net cash from investing activities	535	(1,220)	4,925
Cash Flows From Financing Activities:
Proceeds from (Repayments of) Other Debt	188	18	53
Net change in long-term debt	(2,149)	397	370
Repurchase of common stock	(1,616)	0	0
Proceeds from Issuance of Preferred Stock and Preference Stock	0	3,449	1,683
Redemption of preferred stock	(1,415)	(500)	(1,725)
Cash dividends paid on common and preferred stock	(2,852)	(2,725)	(1,459)
Other, net	(107)	479	(40)
Net Cash Provided by (Used in) Financing Activities	(7,951)	1,118	(1,118)
Cash and Cash Equivalents, Period Increase (Decrease)	(3,844)	1,730	5,160
Cash and Cash Equivalents, at Carrying Value	$ 10,278	$ 14,122	$ 12,392	$ 7,232