Fair Value Measurements - Additional Information (Detail) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)		Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)		Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets		$ 3,358	$ 3,423		$ 3,358	$ 3,423		$ 3,323	$ 3,328	$ 3,497	$ 3,504
Loss severity, trust preferred securities					1.8
Average deviation of implied volatility, foreign currency pair					5.00%
Average deviation of implied volatility, at-the-money equity option					5.00%
Fair Value Liability, Transfers Out of Level 3		143	90		$ 286	211
Fair Value Liability, Transfers Into Level 3		(7)	(22)		(15)	(22)
Fair Value Assets, Transfers Out of Level 3		1	1		$ 0	0
Revaluation period					45 days
Weighted Average [Member] | Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity					75.00%
Weighted Average [Member] | Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity					27.00%
Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets		397	387		$ 397	387
Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets		223	217		223	217
Credit contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets	[1]	188	179		188	179		$ 177	179	$ 192	$ 210
Fair Value Assets, Transfers Out of Level 3	[1]	0	0		0	0
Domestic Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Liability, Transfers Out of Level 3		82	78	[2]	141	179	[2]
Fair Value Liability, Transfers Into Level 3	[2]	(7)	(22)		(15)	(22)
Borrowings [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Liability, Transfers Out of Level 3		61	12	[2]	145	32	[2]
Fair Value Liability, Transfers Into Level 3		0	$ 0	[2]	0	$ 0	[2]
Other liabilities [Member] | Standby Letters of Credit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees on standby letters of credit		$ 52			$ 52				$ 54

[1] Level 3 net derivatives included derivative assets of $397 million and derivative liabilities of $223 million at June 30, 2016 and derivative assets of $387 million and derivative liabilities of $217 million at June 30, 2015.

[2] See Note 11, "Fair Value Option," for additional information.