Accumulated Other Comprehensive Loss - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Tax (benefit) expense included in net unrealized gains (losses), investment securities	$ 136	$ (125)	$ (239)
Tax included in reclassification, investment securities	(19)	(26)	(18)
Tax included in amortization, investment securities	10	16	15
Cumulative effect of new accounting principle in period of adoption, tax	103	0	0
Tax (benefit) expense included in net unrealized gains (losses), fair value option liabilities	(115)	0	0
Tax (benefit) expense included in net unrealized gains (losses), cash flow hedges	(11)	3	(2)
Tax included in reclassification, cash flow hedges	6	6	4
Tax included in net unrealized gains (losses)	$ 1	$ 2	$ 0

Cumulative Effect of New Accounting Principle in Period of Adoption, Tax

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- Definition

Other Comprehensive Income (Loss), Amortization of Unrealized Loss on Transfers from Available-for-Sale to Held-to Maturity Securities, Tax

+ References

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- Definition

Amount of tax expense (benefit) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

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- Definition

Amount, before reclassification adjustment, of tax expense (benefit) for unrealized gain (loss) from increase (decrease) in instrument-specific credit risk on financial liability measured under fair value option.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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- Definition

Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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- Definition

Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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Amount of tax expense (benefit), before reclassification adjustments, related to increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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- Definition

Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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