Fair Value Measurements - Additional Information (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)		Dec. 31, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		$ 3,356		$ 3,328		$ 3,504
Fair value of level 3 liabilities		$ 1,906		2,613		2,615
Loss severity, trust preferred securities		0.85
Average deviation of implied volatility, foreign currency pair		2.00%
Average deviation of implied volatility, at-the-money equity option		5.00%
Fair Value Assets, Transfers Into Level 3		$ 106		(2)
Fair Value Assets, Transfers Out of Level 3		(92)		1
Fair Value Liability, Transfers Into Level 3		(55)		(165)
Fair Value Liability, Transfers Out of Level 3		$ 453		397
Revaluation period		45 days
Weighted Average [Member] | Residential mortgages and home equity mortgages [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity		54.00%
Weighted Average [Member] | Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Inputs, Loss Severity		41.00%
Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		$ 391		346
Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	208		249
Credit contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[2]	193		179		210
Fair Value Assets, Transfers Into Level 3	[2]	0		0
Fair Value Assets, Transfers Out of Level 3	[2]	0		0
Mortgage servicing rights [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		0		140	[3]	159	[3]
Fair Value Assets, Transfers Into Level 3	[3]	0		0
Fair Value Assets, Transfers Out of Level 3		(96)	[2]	0	[3]
Domestic Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities		1,407		1,867	[1]	1,968	[1]
Fair Value Liability, Transfers Into Level 3	[1]	(55)		(162)
Fair Value Liability, Transfers Out of Level 3		212		266	[1]
Borrowings [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities		499		746	[1]	$ 647	[1]
Fair Value Liability, Transfers Into Level 3		0		(3)	[1]
Fair Value Liability, Transfers Out of Level 3		241		131	[1]
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		$ 49		$ 54

[1] See Note 15, "Fair Value Option," for additional information.

[2] Level 3 net derivatives included derivative assets of $391 million and derivative liabilities of $208 million at December 31, 2016 and derivative assets of $346 million and derivative liabilities of $249 million at December 31, 2015.

[3] See Note 9, "Intangible Assets," for additional information.