Fair Value - Schedule of Fair Value Measurements, Assets, Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 2,756	$ 1,288
Total realized and unrealized gain (losses) recorded in revenue	11	(2)
Total realized and unrealized gain (losses) recorded in other comprehensive income	(149)	(4)
Purchases	181	144
Sales	(42)	0
Settlements	(35)	(70)
Transfers into Level 3	0	0
Transfers out of Level 3	0	(12)
Fair value, end of period	2,722	1,344
Change in unrealized gains (losses) related to financial instruments held	12	(1)
Derivative instruments, assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	4	4
Total realized and unrealized gain (losses) recorded in revenue	11	(3)
Total realized and unrealized gain (losses) recorded in other comprehensive income	0	0
Purchases	3	3
Sales	0	0
Settlements	(1)	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, end of period	17	4
Change in unrealized gains (losses) related to financial instruments held	12	(1)
Foreign exchange contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	4	4
Total realized and unrealized gain (losses) recorded in revenue	11	(3)
Total realized and unrealized gain (losses) recorded in other comprehensive income	0	0
Purchases	3	3
Sales	0	0
Settlements	(1)	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, end of period	17	4
Change in unrealized gains (losses) related to financial instruments held	12	(1)
Asset-backed securities, collateralized loan obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	1,820	593
Total realized and unrealized gain (losses) recorded in revenue	0	1
Total realized and unrealized gain (losses) recorded in other comprehensive income	(83)	(2)
Purchases	178	132
Sales	(42)	0
Settlements	(32)	(56)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, end of period	1,841	668
Asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	1,820	593
Total realized and unrealized gain (losses) recorded in revenue	0	1
Total realized and unrealized gain (losses) recorded in other comprehensive income	(83)	(2)
Purchases	178	132
Sales	(42)	0
Settlements	(32)	(56)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, end of period	1,841	668
Non-U.S. debt securities, asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	887	631
Total realized and unrealized gain (losses) recorded in revenue	0	0
Total realized and unrealized gain (losses) recorded in other comprehensive income	(65)	(2)
Purchases	0	9
Sales	0	0
Settlements	(2)	(11)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, end of period	820	627
Non-U.S. debt securities, other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	45	58
Total realized and unrealized gain (losses) recorded in revenue	0	0
Total realized and unrealized gain (losses) recorded in other comprehensive income	(1)	0
Purchases	0	0
Sales	0	0
Settlements	0	(1)
Transfers into Level 3	0	0
Transfers out of Level 3	0	(12)
Fair value, end of period	44	45
Total non-U.S. debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	932	689
Total realized and unrealized gain (losses) recorded in revenue	0	0
Total realized and unrealized gain (losses) recorded in other comprehensive income	(66)	(2)
Purchases	0	9
Sales	0	0
Settlements	(2)	(12)
Transfers into Level 3	0	0
Transfers out of Level 3	0	(12)
Fair value, end of period	864	672
Collateralized mortgage obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period		2
Total realized and unrealized gain (losses) recorded in revenue		0
Total realized and unrealized gain (losses) recorded in other comprehensive income		0
Purchases		0
Sales		0
Settlements		(2)
Transfers into Level 3		0
Transfers out of Level 3		0
Fair value, end of period		0
Investment securities available-for-sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	2,752	1,284
Total realized and unrealized gain (losses) recorded in revenue	0	1
Total realized and unrealized gain (losses) recorded in other comprehensive income	(149)	(4)
Purchases	178	141
Sales	(42)	0
Settlements	(34)	(70)
Transfers into Level 3	0	0
Transfers out of Level 3	0	(12)
Fair value, end of period	$ 2,705	$ 1,340

Change in Unrealized Gains (Losses) Related to Financial Instruments, Assets, Held at Period End

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
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- Definition

Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
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-Section 50
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- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
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- Definition

Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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