Trading Securities (Detail) - USD ($) $ in Millions		Jun. 30, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	[1]	$ 6,850	$ 6,119
Trading liabilities		1,245	1,263
US Treasury Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		531	538
Trading liabilities		473	503
US Government Agencies Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		396	588
US States and Political Subdivisions Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		54	30
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		826	553
Trading liabilities		3	37
Collateralized Loan Obligations [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		3	2
Corporate Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		499	468
Trading liabilities		311	259
Commercial Paper [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		139	67
Equity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets		53	66
Derivative Financial Instruments, Assets [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	[2]	1,669	1,152
Loans [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	[3]	2,680	2,655
Derivative Financial Instruments, Liabilities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading liabilities	[2]	$ 458	$ 464

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,282 million and $1,377 million at June 30, 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.