Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015
Derivative Liability, Fair Value, Gross Liability	$ 4,902		$ 4,428
Derivative Asset, Fair Value, Gross Asset	4,514		4,465
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	138
Netted counterparty balance [Member]
Fair Value, Concentration of Risk, Derivative Instruments, Assets	774		896
Derivative Asset, Fair Value of Collateral	339		463
Derivative Credit Risk Valuation Adjustment, Derivative Assets	6		4
Derivative liability positions containing provisions conditioned on downgrades [Member]
Derivative Liability, Fair Value, Gross Liability	1,100		1,100
Netted counterparty balance gains [Member]
Fair Value, Concentration of Risk, Derivative Instruments, Assets	1,100		1,400
Additional Termination Event [Member]
Derivative Liability, Fair Value, Gross Liability	1
Credit Default Swap, Buying Protection [Member]
Credit Risk Derivatives, at Fair Value, Net	3		1
Derivative, Notional Amount	135		150
Total Return Swap [Member]
Derivative Liability, Fair Value, Gross Liability	31		52
Derivative, Notional Amount	2,100		2,200
Derivative Asset, Fair Value, Gross Asset	34		57
Collateral Already Posted, Aggregate Fair Value	450		492
Financial Guarantee [Member]
Credit Derivative, Maximum Exposure, Undiscounted	$ 95		$ 55
Weighted Average of Maturities of Cash Flow Hedges	8 years 6 months		5 years 7 months
Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Derivative Liability, Fair Value, Gross Liability	$ 265	[1]	$ 11	[2]
Derivative Asset, Fair Value, Gross Asset	$ 34	[1]	$ 130	[2]
Weighted Average of Maturities of Cash Flow Hedges	4 years 1 month		3 years 3 months
Credit Support Annex [Member]
Derivative Liability, Fair Value, Gross Liability	$ 1,100
Collateral Already Posted, Aggregate Fair Value	1,100
Additional Collateral, Aggregate Fair Value	$ 5
Minimum [Member] | Financial Guarantee [Member]
Derivative, Remaining Maturity	1 year		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	$ 13
Maximum [Member] | Financial Guarantee [Member]
Derivative, Remaining Maturity	31 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.