Fair Value of Financial Instruments - Reconciliation of Level 3 Financial Instruments (Details) - Level 3 - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 39	$ 4
Contracts added from acquisitions	(3)	12
Included in earnings
Included in earnings	(26)	(21)
Included in OCI	0
Purchases	40	41
Sale	(19)
Transfers into Level 3	2	5
Transfers out of Level 3	5	(2)
Ending balance	38	39
Gains (Losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held at the end of period	17	(17)
Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	19	19
Contracts added from acquisitions	0	0
Included in earnings
Included in earnings	0	0
Included in OCI	0
Purchases	0	0
Sale	(19)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	0	19
Gains (Losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held at the end of period	0	0
Derivative
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	20	(15)
Contracts added from acquisitions	(3)	12
Included in earnings
Included in earnings	(26)	(21)
Included in OCI	0
Purchases	40	41
Sale	0
Transfers into Level 3	2	5
Transfers out of Level 3	5	(2)
Ending balance	38	20
Gains (Losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held at the end of period	$ 17	$ (17)

No definition available.

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- Definition

Fair Value, Net Derivative Asset (Liability) Measured On Recurring Basis, Unobservable Inputs Reconciliation, Acquisition

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No definition available.

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

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- Definition

Amount of unrealized gain (loss) recognized in income for derivative asset (liability) after deduction of derivative liability (asset), measured at fair value using unobservable input (level 3) and still held.

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- Definition

Amount of gain (loss) recognized in income from derivative asset (liability) after deduction of derivative liability (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
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- Definition

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

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- Definition

Amount of purchases of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (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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Amount of sales of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (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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Amount of transfers of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset) into level 3 of the fair value hierarchy.

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Amount of transfers of financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset) out of level 3 of the fair value hierarchy.

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Fair value of financial instrument classified as derivative asset (liability) after deduction of derivative liability (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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