Derivative Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Derivative Liability, Fair Value, Gross Liability	5,728,000,000	$ 5,577,000,000
Derivative Asset, Fair Value, Gross Asset	6,067,000,000	5,839,000,000
Cash Flow Hedging
Deferred net gains on derivatives that are recorded in AOCI are expected to be reclassified to net interest income over the next twelve months in connection with the recognition of interest income or interest expense on these hedged items	208,000,000
written risk participations [Member]
Minimum Term of Credit Risk Derivatives	0 years
Maximum Term of Credit Risk Derivatives	8 years
Weighted Average Term of Credit Risk Derivatives	5
Credit and Market Risk
Derivative asset positions	1,200,000,000	1,100,000,000
Net derivative asset positions to which the Company was exposed to risk of its counterparties, netted by counterparty where formal netting arrangements exist	1,800,000,000	1,500,000,000
Collateral Held by The Company Against Derivative Asset Positions	602,000,000	386,000,000
Adjusted the fair value of its net derivative asset position for estimates of counterparty credit risk	3,000,000	7,000,000
Derivative Liability, Fair Value, Gross Liability	1,200,000,000	1,100,000,000
Credit and Market Risk | Additional Termination Event [Member]
Derivative Liability, Fair Value, Gross Liability	1,000,000
Credit and Market Risk | Additional Termination Event [Member] | Credit Downgrade [Member]
Derivative Liability, Fair Value, Gross Liability	29,000,000
Credit and Market Risk | Credit Support Annex
Derivative Liability, Fair Value, Gross Liability	1,200,000,000
Derivative Liability, Fair Value of Collateral	1,100,000,000
Credit and Market Risk | Credit Support Annex | Credit Downgrade [Member]
Posted collateral	22,000,000
Credit Default Swap
Maximum Term of Credit Risk Derivatives	5 years	4 years
Maximum exposure	284,000,000	20,000,000
Derivative, Notional Amount	494,000,000	190,000,000
Credit Risk Derivatives, at Fair Value, Net	9,000,000	5,000,000
Credit Derivatives Swap Participation
Maximum exposure		31,000,000
Cash Flow Derivatives Hedges [Member]
Derivative, Lower Remaining Maturity Range	0 years
Derivative, Higher Remaining Maturity Range	5 years
Weighted Average of Maturities of Cash Flow Hedges	2.5
Total Return Swap
Derivative Liability, Fair Value, Gross Liability	15,000,000	14,000,000
Derivative, Notional Amount		2,300,000,000
Derivative Asset, Fair Value, Gross Asset	20,000,000	19,000,000
Collateral held	381,000,000	373,000,000
Derivatives Sold | Credit Default Swap
Credit Risk Derivatives, at Fair Value, Net	3,000,000	1,000,000
Interest Income (Expense), Net [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	19,000,000		$ 26,000,000