The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

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Maximum potential amount of future undiscounted payments that could be required under the credit derivative, before reduction for potential recoveries under recourse or collateralization provisions.

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Fair value of securities received as collateral against derivative assets.

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Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Derivative Liability, Fair Value, Gross Liability	$ 3,031		$ 3,031		$ 2,716
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	158		158
Derivative Asset, Fair Value, Gross Asset	3,878		3,878		2,631
Netted counterparty balance [Member]
Fair Value, Concentration of Risk, Derivative Instruments, Assets	1,400		1,400		541
Derivative Asset, Fair Value of Collateral	374		374		350
Netted counterparty balance gains [Member]
Fair Value, Concentration of Risk, Derivative Instruments, Assets	1,800		1,800		891
Derivative liability positions containing provisions conditioned on downgrades [Member]
Derivative Liability, Fair Value, Gross Liability	1,400		1,400		$ 589
Additional Termination Event [Member]
Derivative Liability, Fair Value, Gross Liability	1		1
Additional Termination Event [Member] \| Maximum [Member]
Derivative Liability, Fair Value, Gross Liability	19		19
Credit Support Annex [Member]
Derivative Liability, Fair Value, Gross Liability	1,400		1,400
Collateral Already Posted, Aggregate Fair Value	958		958
Credit Support Annex [Member] \| Moody's, Baa3 Rating [Member]
Additional Collateral, Aggregate Fair Value	1		1
Credit Support Annex [Member] \| Moody's, Ba1 Rating [Member]
Additional Collateral, Aggregate Fair Value	8		$ 8
Financial Guarantee [Member]
Derivative, Average Remaining Maturity			6 years		5 years 10 months 24 days
Credit Derivative, Maximum Exposure, Undiscounted	281		$ 281		$ 217
Financial Guarantee [Member] \| Minimum [Member]
Derivative, Remaining Maturity			1 year		1 year
Financial Guarantee [Member] \| Maximum [Member]
Derivative, Remaining Maturity			11 years		10 years
Interest Rate Contract [Member] \| Cash Flow Hedging [Member]
Derivative, Average Remaining Maturity			3 years 3 months 18 days		2 years 6 months
Interest Rate Contract [Member] \| Minimum [Member] \| Cash Flow Hedging [Member]
Derivative, Remaining Maturity			1 year		1 year
Interest Rate Contract [Member] \| Maximum [Member] \| Cash Flow Hedging [Member]
Derivative, Remaining Maturity			7 years		5 years
Interest Income [Member] \| Loans Held-For-Investment [Member] \| Interest Rate Contract [Member] \| Cash Flow Hedging [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ 61	$ (48)	$ 266	$ (274)