Trading Securities (Detail) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	[1]	$ 6,259	$ 5,506
Trading liabilities		1,609	1,604
US Treasury Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI		258	262
Trading liabilities		873	801
US Government Agencies Debt Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI		281	188
US States and Political Subdivisions Debt Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI		33	54
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI		814	860
Trading liabilities		3	3
Corporate Debt Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI		889	700
Trading liabilities		456	385
Commercial Paper [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI		283	190
Equity Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI		71	73
Trading liabilities		13	5
Derivative Financial Instruments, Assets [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	[2]	1,028	639
Loans [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	[3]	2,602	2,540
Derivative Financial Instruments, Liabilities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading liabilities	[2]	$ 264	$ 410

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,382 million and $1,442 million at March 31, 2019 and December 31, 2018, respectively.

[2] Amounts include the impact of offsetting cash collateral received from and paid to the same derivative counterparties, and the impact of netting derivative assets and derivative liabilities when a legally enforceable master netting agreement or similar agreement exists.

[3] Includes loans related to TRS.