Derivatives and Hedging Activities - Derivative Instrument Cash Flow Hedge Earning Recognized by Income Statement Location (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	$ (34)	$ (15)	$ (165)	$ (25)
Net Gains (Losses) Reclassified From OCI Into Income(a)	(17)	0	(44)	18
Net Gains (Losses) Recognized in Other Income(a)	0	0	0	0
Interest Income [Member] \| Interest Rate [Member] \| Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	(32)	(1)	(178)	(1)
Net Gains (Losses) Reclassified From OCI Into Income(a)	(15)	1	(42)	21
Net Gains (Losses) Recognized in Other Income(a)	0	0	0	0
Interest Expense [Member] \| Interest Rate [Member] \| Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	(1)	(1)	3	(1)
Net Gains (Losses) Reclassified From OCI Into Income(a)	2	(1)	(2)	(3)
Net Gains (Losses) Recognized in Other Income(a)	0	0	0	0
Underwriting Discounts Fees And Commissions [Member] \| Interest Rate [Member] \| Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	1	(1)	2	(1)
Net Gains (Losses) Reclassified From OCI Into Income(a)	0	0	0	0
Net Gains (Losses) Recognized in Other Income(a)	0	0	0	0
Other Income [Member] \| Foreign Exchange [Member] \| Net Investment Hedges [Member]
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	(2)	(12)	8	(22)
Net Gains (Losses) Reclassified From OCI Into Income(a)	0	0	0	0
Net Gains (Losses) Recognized in Other Income(a)	$ 0	$ 0	$ 0	$ 0

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

+ References

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Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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