Trading Securities (Detail) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	[1]	$ 6,067	$ 6,119
Trading liabilities		1,351	1,263
US Treasury Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		539	538
Trading liabilities		697	503
US Government Agencies Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		480	588
US States and Political Subdivisions Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		134	30
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		567	553
Trading liabilities		1	37
Collateralized Loan Obligations [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		1	2
Corporate Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		656	468
Trading liabilities		255	259
Commercial Paper [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		140	67
Equity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		49	66
Derivative Financial Instruments, Assets [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	[2]	984	1,152
Loans [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	[3]	2,517	2,655
Derivative Financial Instruments, Liabilities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading liabilities	[2]	$ 398	$ 464

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,437 million and $1,377 million at December 31, 2016 and December 31, 2015, 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.