Employee Benefits - Cash Flows (Details) $ in Millions	Dec. 31, 2019 USD ($)
Retirement Plans
Information about the expected cash flows for retirement and post-retirement plans and impact of the Medicare subsidy
2020, Net payments	$ 63
2021, Net payments	66
2022, Net payments	69
2023, Net payments	72
2024, Net payments	75
2025-2029, Net payments	413
Postretirement Plans
Information about the expected cash flows for retirement and post-retirement plans and impact of the Medicare subsidy
2020, Gross payments	7
2021, Gross payments	6
2022, Gross payments	6
2023, Gross payments	5
2024, Gross payments	5
2025-2029, Gross payments	17
2020, Retiree Contributions	(2)
2021, Retiree Contributions	(2)
2022, Retiree Contributions	(2)
2023, Retiree Contributions	(1)
2024, Retiree Contributions	(1)
2025-2029, Retiree Contributions	(6)
2020, Medicare subsidy (less than $1 million)	0
2021, Medicare subsidy (less than $1 million)	0
2022, Medicare subsidy (less than $1 million)	0
2023, Medicare subsidy (less than $1 million)	0
2024, Medicare subsidy (less than $1 million)	0
2025-2029, Medicare subsidy (less than $1 million)	0
2020, Net payments	5
2021, Net payments	4
2022, Net payments	4
2023, Net payments	4
2024, Net payments	4
2025-2029, Net payments	11
Medicare subsidy, expected payments for all years (less than)	$ 1

Defined benefit plan expected future benefit payments gross in five fiscal years thereafter.

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Defined benefit plan expected future benefit payments gross in year five.

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Defined benefit plan expected future benefit payments gross in year four.

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Defined benefit plan expected future benefit payments gross in year one.

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Defined benefit plan expected future benefit payments gross in year three.

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Defined benefit plan expected future benefit payments gross in year two.

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Defined benefit plan expected future benefit payments retiree contributions in five fiscal years thereafter.

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Defined benefit plan expected future benefit payments retiree contributions in year five.

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Defined benefit plan expected future benefit payments retiree contributions in year four.

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Defined Benefit Plan, Expected Future Prescription Drug Subsidy Receipt, For All Years

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

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

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

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

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

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Amount of prescription drug subsidy receipts expected after fifth fiscal year following latest fiscal year.

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