Securities - Amortized Cost and Fair Value of Asset Backed Securities (Detail) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020
Securities available-for-sale:
Amortized Cost		$ 35,356	$ 39,636
Allowance for Credit Losses		(1)	(1)
Unrealized Gains		305	1,109
Unrealized Losses		(362)	(72)
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)	[1]	35,298	40,672
Securities held-to-maturity:
Amortized Cost		5,204	8,983
Allowance for Credit Losses		(1)	(2)
Unrealized Gains		157	388
Unrealized Losses		(1)	0
Fair Value		5,359	9,369
U.S. Treasury
Securities available-for-sale:
Amortized Cost		9,490	16,087
Allowance for Credit Losses		0	0
Unrealized Gains		144	608
Unrealized Losses		(72)	(47)
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		9,562	16,648
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Securities available-for-sale:
Amortized Cost		7,365	5,986
Allowance for Credit Losses		0	0
Unrealized Gains		114	280
Unrealized Losses		(115)	(2)
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		7,364	6,264
Securities held-to-maturity:
Amortized Cost		684	1,137
Allowance for Credit Losses		0	0
Unrealized Gains		21	44
Unrealized Losses		0	0
Fair Value		705	1,181
Collateralized Mortgage Obligations, Issued by U.S. Government Sponsored Enterprises
Securities available-for-sale:
Amortized Cost		1,787	1,676
Allowance for Credit Losses		0	0
Unrealized Gains		8	19
Unrealized Losses		(48)	(2)
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		1,747	1,693
Securities held-to-maturity:
Amortized Cost		492	780
Allowance for Credit Losses		0	0
Unrealized Gains		26	53
Unrealized Losses		0	0
Fair Value		518	833
Direct Agency Obligations U S Government Sponsored Enterprises
Securities available-for-sale:
Amortized Cost		1,775	1,236
Allowance for Credit Losses		0	0
Unrealized Gains		16	17
Unrealized Losses		(4)	0
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		1,787	1,253
Mortgage-backed Securities, Issued or Guaranteed by US Government Agency
Securities available-for-sale:
Amortized Cost		8,489	6,993
Allowance for Credit Losses		0	0
Unrealized Gains		7	152
Unrealized Losses		(66)	0
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		8,430	7,145
Securities held-to-maturity:
Amortized Cost		1,104	1,947
Allowance for Credit Losses		0	0
Unrealized Gains		24	76
Unrealized Losses		0	0
Fair Value		1,128	2,023
Collateralized Mortgage Obligations, Issued or Guaranteed by US Government Agency
Securities available-for-sale:
Amortized Cost		3,730	2,093
Allowance for Credit Losses		0	0
Unrealized Gains		7	22
Unrealized Losses		(49)	(11)
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		3,688	2,104
Securities held-to-maturity:
Amortized Cost		2,915	5,107
Allowance for Credit Losses		0	0
Unrealized Gains		85	212
Unrealized Losses		(1)	0
Fair Value		2,999	5,319
Direct Agency Obligations, Issued or Guaranteed by US Government Agency
Securities available-for-sale:
Amortized Cost		282	296
Allowance for Credit Losses		0	0
Unrealized Gains		6	5
Unrealized Losses		0	0
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		288	301
Home equity
Securities available-for-sale:
Amortized Cost		20	28
Allowance for Credit Losses		(1)	(1)
Unrealized Gains		0	0
Unrealized Losses		0	0
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		19	27
Other
Securities available-for-sale:
Amortized Cost		107	114
Allowance for Credit Losses		0	0
Unrealized Gains		0	0
Unrealized Losses		(6)	(10)
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		101	104
Foreign debt securities
Securities available-for-sale:
Amortized Cost		2,311	5,127
Allowance for Credit Losses		0	0
Unrealized Gains		3	6
Unrealized Losses		(2)	0
Securities available-for-sale (includes amortized cost of $35.4 billion and $39.6 billion at December 31, 2021 and 2020, respectively, an allowance for credit losses of $1 million at both December 31, 2021 and 2020, and $2.4 billion and $2.1 billion pledged to creditors at December 31, 2021 and 2020, respectively)		2,312	5,133
Obligations of U.S. states and political subdivisions
Securities held-to-maturity:
Amortized Cost		8	10
Allowance for Credit Losses		0	0
Unrealized Gains		0	1
Unrealized Losses		0	0
Fair Value		8	11
Asset-backed securities collateralized by residential mortgages
Securities held-to-maturity:
Amortized Cost		1	2
Allowance for Credit Losses		(1)	(2)
Unrealized Gains		1	2
Unrealized Losses		0	0
Fair Value		$ 1	$ 2

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at December 31, 2021 and 2020. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 27, "Variable Interest Entities," for additional information. At December 31,20212020(in millions)AssetsLoans$46 $10 Other assets55 79 Total assets$101 $89 LiabilitiesInterest, taxes and other liabilities$9 $10 Total liabilities$9 $10