Derivative Financial Instruments and Hedging Activities - Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Fair value of assets (liabilities) available for offset	$ 701	$ 302
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	131,201	108,673
Derivative asset, Fair value	1,706	636
Collateral available for netting against liability positions	274	89
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	1,209	519
Cash held for netting against asset positions	778	210
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Other Assets [Member] \| Interest Rate Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	10,894	9,458
Derivative asset, Fair value	609	234
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Other Assets [Member] \| Foreign Currency Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	1,797	1,796
Derivative asset, Fair value	26	22
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Other Liabilities [Member] \| Interest Rate Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	0	23
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Other Liabilities [Member] \| Foreign Currency Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	68	71
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Assets [Member] \| Interest Rate Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	964	590
Derivative asset, Fair value	0	0
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Assets [Member] \| Foreign Currency Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	5,143	4,429
Derivative asset, Fair value	26	40
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Liabilities [Member] \| Interest Rate Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	32	6
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Liabilities [Member] \| Foreign Currency Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	302	119
Not Designated as Hedging Instrument [Member] \| Other Assets [Member] \| Interest Rate Contracts [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	112,403	92,400
Derivative asset, Fair value	1,045	340
Not Designated as Hedging Instrument [Member] \| Other Liabilities [Member] \| Interest Rate Contracts [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair value	$ 807	$ 300

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

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- Definition

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

+ References

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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.

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