Derivative Financial Instruments and Hedging Activities - Derivative Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Fair value of assets (liabilities) available for offset	$ 320	$ 284
Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	113,871	98,000
Derivative asset, Fair value	502	553
Collateral available for netting	451	299
Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	869	497
Cash held	30	25
Derivatives Designated as Hedges [Member] \| Assets [Member] \| Fair Value Hedging [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	9,533	11,110
Derivative asset, Fair value	42	2
Derivatives Designated as Hedges [Member] \| Assets [Member] \| Fair Value Hedging [Member] \| Fair Value, Inputs, Level 2 [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	1,829	0
Derivative asset, Fair value	37	0
Derivatives Designated as Hedges [Member] \| Assets [Member] \| Cash Flow Hedging [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	768	2,177
Derivative asset, Fair value	8	15
Derivatives Designated as Hedges [Member] \| Assets [Member] \| Cash Flow Hedging [Member] \| Fair Value, Inputs, Level 2 [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	2,075	1,574
Derivative asset, Fair value	43	103
Derivatives Designated as Hedges [Member] \| Liabilities [Member] \| Fair Value Hedging [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	231	290
Derivatives Designated as Hedges [Member] \| Liabilities [Member] \| Fair Value Hedging [Member] \| Fair Value, Inputs, Level 2 [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	60	0
Derivatives Designated as Hedges [Member] \| Liabilities [Member] \| Cash Flow Hedging [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	0	0
Derivatives Designated as Hedges [Member] \| Liabilities [Member] \| Cash Flow Hedging [Member] \| Fair Value, Inputs, Level 2 [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	58	0
Derivatives not Designated as Hedges [Member] \| Assets [Member] \| Fair Value, Inputs, Level 2 [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	0	1,201
Derivative asset, Fair value	0	104
Derivatives not Designated as Hedges [Member] \| Assets [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	99,666	81,938
Derivative asset, Fair value	372	329
Derivatives not Designated as Hedges [Member] \| Liabilities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	0	0
Derivatives not Designated as Hedges [Member] \| Liabilities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	$ 520	$ 207

Derivative Assets (Liabilities), Net, Fair Value, Amount Not Offset Against Collateral

No definition available.

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- Definition

Nominal or face amount used to calculate payments on the derivative asset.

+ References

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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- Definition

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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- Definition

Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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