Derivative Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Net unrealized pre-tax gains related to hedged loans held for sale, commitments to originate loans for sale and commitments to sell loans	$ 28,000,000	$ 18,000,000
Aggregate fair value of derivative financial instruments in a liability position	34,000,000	59,000,000
Net liability positions with counterparties	30,000,000	55,000,000
Aggregate fair value of derivative financial instruments in asset position	15,000,000	23,000,000
Net fair value of derivative financial instruments in a net asset position	11,000,000	19,000,000
Collateral relating to net asset positions	9,000,000	22,000,000
Counterparties [Member]
Derivative [Line Items]
Post collateral requirements relating to positions	27,000,000	52,000,000
Clearinghouse Credit Facilities [Member]
Derivative [Line Items]
Post collateral requirements relating to positions		47,000,000
Aggregate fair value of derivative financial instruments in a net liability position		50,000,000
Net fair value of derivative financial instruments in a net asset position	63,000,000
Collateral relating to net asset positions	81,000,000
Amount of initial margin posted	111,000,000	52,000,000
Interest Rate Swap Agreements [Member]
Derivative [Line Items]
Increase in net interest income due to interest rate swap agreements	37,000,000	44,000,000	$ 45,000,000
Average notional amounts of interest rate swap agreements impacting net interest income, contract entered into for interest rate risk management purposes	1,400,000,000	1,400,000,000	$ 1,400,000,000
Notional amounts of derivative contracts entered into for trading account purposes	900,000,000
Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amounts of derivative contracts entered into for trading account purposes	21,600,000,000	18,400,000,000
Foreign Currency and Other Option and Futures Contracts [Member]
Derivative [Line Items]
Notional amounts of derivative contracts entered into for trading account purposes	471,000,000,000	$ 1,600,000,000
Credit Risk Derivative [Member]
Derivative [Line Items]
Aggregate fair value of derivative financial instruments in a net liability position	2,000,000
Fair value of additional collateral to be posted for derivative financial instruments	$ 2,000,000