Derivative Instruments and Hedging Activities (Fair Value Amounts of Derivative Instruments Reported on our Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	$ 10	$ 64
Fair value of derivative contracts in payable position	7	5
Derivative, notional amount	14,638	32,489
Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	0	62
Fair value of derivative contracts in payable position	3	3
Derivative, notional amount	11,346	31,358
Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	10	2
Fair value of derivative contracts in payable position	4	2
Derivative, notional amount	3,292	1,131
Interest rate contracts \| Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	10	2
Fair value of derivative contracts in payable position	2	0
Derivative, notional amount	3,188	1,019
Interest rate swaps \| Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	0	0
Fair value of derivative contracts in payable position	0	0
Derivative, notional amount	11,215	17,101
Interest rate purchased options \| Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	0	62
Fair value of derivative contracts in payable position	0	0
Derivative, notional amount	0	14,100
Interest rate purchased options \| Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	2	0
Fair value of derivative contracts in payable position	0	0
Derivative, notional amount	1,152	416
Interest rate futures and forwards \| Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	0	0
Fair value of derivative contracts in payable position	0	0
Derivative, notional amount	63	81
Interest rate written options \| Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	8	2
Fair value of derivative contracts in payable position	2	0
Derivative, notional amount	1,503	522
Foreign exchange contracts \| Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	0	0
Fair value of derivative contracts in payable position	2	2
Derivative, notional amount	104	112
Foreign exchange forwards \| Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	0	0
Fair value of derivative contracts in payable position	3	3
Derivative, notional amount	131	157
Foreign exchange futures and forwards \| Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	0	0
Fair value of derivative contracts in payable position	2	2
Derivative, notional amount	104	112
Interest rate swaps \| Interest rate contracts \| Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative contracts in receivable position	0	0
Fair value of derivative contracts in payable position	0	0
Derivative, notional amount	$ 470	$ 0

Fair value, before 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 elected not to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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- Definition

Fair value, before 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 elected not to be offset.

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

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