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Pension, Savings, and Other Employee Benefits - Schedule of Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Net actuarial (gain) loss arising during measurement period	$ (8)	$ (14)
Items amortized during the measurement period:
Actuarial (gain)/loss	(13)	(10)
Total recognized in other comprehensive income	(21)	(24)
Other Benefits
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Net actuarial (gain) loss arising during measurement period	3	5
Items amortized during the measurement period:
Actuarial (gain)/loss	0	0
Total recognized in other comprehensive income	$ 3	$ 5

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- Definition

Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) During Measurement Period [Abstract]

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Amount, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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Amount, before tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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