Securities - Amortized Cost and Fair Value of Asset Backed Securities (Detail) - USD ($)		Sep. 30, 2024	Dec. 31, 2023
Securities available-for-sale:
Amortized Cost		$ 27,746,000,000	$ 27,980,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		20,000,000	26,000,000
Unrealized Losses		(1,824,000,000)	(2,310,000,000)
Fair Value	[1]	25,942,000,000	25,696,000,000
Securities held-to-maturity:
Amortized Cost		17,238,000,000	15,076,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		103,000,000	47,000,000
Unrealized Losses		(305,000,000)	(434,000,000)
Fair Value		17,036,000,000	14,689,000,000
U.S. Treasury
Securities available-for-sale:
Amortized Cost		9,318,000,000	7,489,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		13,000,000	22,000,000
Unrealized Losses		(219,000,000)	(225,000,000)
Fair Value		9,112,000,000	7,286,000,000
Securities held-to-maturity:
Amortized Cost		2,797,000,000	1,917,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		7,000,000	1,000,000
Unrealized Losses		(6,000,000)	(18,000,000)
Fair Value		2,798,000,000	1,900,000,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Securities available-for-sale:
Amortized Cost		3,325,000,000	5,864,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		0	0
Unrealized Losses		(565,000,000)	(845,000,000)
Fair Value		2,760,000,000	5,019,000,000
Securities held-to-maturity:
Amortized Cost		1,020,000,000	1,069,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		0	0
Unrealized Losses		(46,000,000)	(68,000,000)
Fair Value		974,000,000	1,001,000,000
Collateralized Mortgage Obligations, Issued by U.S. Government Sponsored Enterprises
Securities available-for-sale:
Amortized Cost		1,349,000,000	1,436,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		0	0
Unrealized Losses		(265,000,000)	(300,000,000)
Fair Value		1,084,000,000	1,136,000,000
Securities held-to-maturity:
Amortized Cost		257,000,000	297,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		4,000,000	3,000,000
Unrealized Losses		(10,000,000)	(16,000,000)
Fair Value		251,000,000	284,000,000
Direct Agency Obligations U S Government Sponsored Enterprises
Securities available-for-sale:
Amortized Cost		1,406,000,000	1,719,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		1,000,000	0
Unrealized Losses		(7,000,000)	(38,000,000)
Fair Value		1,400,000,000	1,681,000,000
Mortgage-backed Securities, Issued or Guaranteed by US Government Agency
Securities available-for-sale:
Amortized Cost		5,430,000,000	5,804,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		2,000,000	1,000,000
Unrealized Losses		(318,000,000)	(378,000,000)
Fair Value		5,114,000,000	5,427,000,000
Securities held-to-maturity:
Amortized Cost		11,594,000,000	10,043,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		92,000,000	43,000,000
Unrealized Losses		(130,000,000)	(180,000,000)
Fair Value		11,556,000,000	9,906,000,000
Collateralized Mortgage Obligations, Issued or Guaranteed by US Government Agency
Securities available-for-sale:
Amortized Cost		2,668,000,000	2,865,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		0	0
Unrealized Losses		(438,000,000)	(506,000,000)
Fair Value		2,230,000,000	2,359,000,000
Securities held-to-maturity:
Amortized Cost		1,567,000,000	1,745,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		0	0
Unrealized Losses		(113,000,000)	(152,000,000)
Fair Value		1,454,000,000	1,593,000,000
Direct Agency Obligations, Issued or Guaranteed by US Government Agency
Securities available-for-sale:
Amortized Cost		167,000,000	215,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		3,000,000	3,000,000
Unrealized Losses		0	(3,000,000)
Fair Value		170,000,000	215,000,000
Home equity asset-backed securities
Securities available-for-sale:
Amortized Cost		11,000,000	13,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		0	0
Unrealized Losses		(1,000,000)	(1,000,000)
Fair Value		10,000,000	12,000,000
Other asset-backed securities
Securities available-for-sale:
Amortized Cost		102,000,000	103,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		0	0
Unrealized Losses		(10,000,000)	(11,000,000)
Fair Value		92,000,000	92,000,000
Foreign debt securities
Securities available-for-sale:
Amortized Cost		3,970,000,000	2,472,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		1,000,000	0
Unrealized Losses		(1,000,000)	(3,000,000)
Fair Value		3,970,000,000	2,469,000,000
Obligations of U.S. states and political subdivisions
Securities held-to-maturity:
Amortized Cost		3,000,000	4,000,000
Allowance for Credit Losses		0	0
Unrealized Gains		0	0
Unrealized Losses		0	0
Fair Value		$ 3,000,000	4,000,000
Asset-backed securities collateralized by residential mortgages
Securities held-to-maturity:
Amortized Cost			1,000,000
Allowance for Credit Losses			0
Unrealized Gains			0
Unrealized Losses			0
Fair Value			$ 1,000,000

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at September 30, 2024 and December 31, 2023. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 15, "Variable Interest Entities," for additional information. September 30, 2024December 31, 2023(in millions)AssetsOther assets$13 $23 Total assets$13 $23 LiabilitiesInterest, taxes and other liabilities$21 $17 Total liabilities$21 $17