Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016		Jun. 30, 2015	Dec. 31, 2015
Derivative Liability, Fair Value, Gross Liability	$ 5,891			$ 4,428
Derivative Asset, Fair Value, Gross Asset	6,598			4,465
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	215
Netted counterparty balance [Member]
Fair Value, Concentration of Risk, Derivative Instruments, Assets	1,300			896
Derivative Asset, Fair Value of Collateral	916			463
Derivative Credit Risk Valuation Adjustment, Derivative Assets	24			4
Liabilities, Fair Value Adjustment	11
Netted counterparty balance gains [Member]
Fair Value, Concentration of Risk, Derivative Instruments, Assets	2,200			1,400
Derivative liability positions containing provisions conditioned on downgrades [Member]
Derivative Liability, Fair Value, Gross Liability	1,400			1,100
Additional Termination Event [Member]
Derivative Liability, Fair Value, Gross Liability	1
Credit Support Annex
Derivative Liability, Fair Value, Gross Liability	1,400
Collateral Already Posted, Aggregate Fair Value	1,300
Additional Collateral, Aggregate Fair Value	20
Credit Default Swap, Selling Protection [Member]
Credit Risk Derivatives, at Fair Value, Net	0			0
Credit Default Swap, Buying Protection [Member]
Credit Risk Derivatives, at Fair Value, Net	2			1
Derivative, Notional Amount	185			150
Total Return Swap [Member]
Derivative Liability, Fair Value, Gross Liability	15			52
Collateral Already Posted, Aggregate Fair Value	481			492
Derivative, Notional Amount	2,200			2,200
Derivative Asset, Fair Value, Gross Asset	19			57
Financial Guarantee [Member]
Credit Derivative, Maximum Exposure, Undiscounted	$ 91			55
Weighted Average of Maturities of Cash Flow Hedges	9 years 8 months		5 years 7 months
Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Derivative Liability, Fair Value, Gross Liability	$ 0			11	[1]
Derivative Asset, Fair Value, Gross Asset	$ 477	[2]		$ 130	[1]
Weighted Average of Maturities of Cash Flow Hedges	4 years		3 years 3 months
Minimum [Member] | Financial Guarantee [Member]
Derivative, Remaining Maturity	0 years		1 year
Minimum [Member] | Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Derivative, Remaining Maturity	1 year		1 year
Maximum [Member] | Additional Termination Event [Member]
Derivative Liability, Fair Value, Gross Liability	$ 12
Maximum [Member] | Financial Guarantee [Member]
Derivative, Remaining Maturity	10 years		8 years
Maximum [Member] | Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Derivative, Remaining Maturity	6 years		7 years

[1] See “Cash Flow Hedges” in this Note for further discussion.

[2] See “Cash Flow Hedges” in this Note for further discussion.