Long-term Employee Benefits (Cash Flows Defined Benefit Plans) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2021	$ 10
2022	10
2023	13
2024	15
2025	15
2026 to 2030	98
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	20	$ 19	$ 15
Estimated future employer contributions in next fiscal year	$ 16

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Amount of benefit for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in next fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in fifth fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in fourth fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in third fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in second fiscal year following current fiscal year.

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Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year.

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