Employee Benefits - Cash Flows (Details) $ in Millions	Dec. 31, 2016 USD ($)
Retirement Plans
Information about the expected cash flows for retirement and post-retirement plans and impact of the Medicare subsidy
2017, Net payments	$ 88
2018, Net payments	90
2019, Net payments	93
2020, Net payments	96
2021, Net payments	98
2022-2026, Net payments	527
Postretirement Plans
Information about the expected cash flows for retirement and post-retirement plans and impact of the Medicare subsidy
2017, Gross payments	12
2018, Gross payments	11
2019, Gross payments	10
2020, Gross payments	9
2021, Gross payments	8
2022-2026, Gross payments	30
2017, Retiree Contributions	(4)
2018, Retiree Contributions	(4)
2019, Retiree Contributions	(3)
2020, Retiree Contributions	(3)
2021, Retiree Contributions	(3)
2022-2026, Retiree Contributions	(12)
2017, Medicare subsidy	0
2018, Medicare subsidy	0
2019, Medicare subsidy	0
2020, Medicare subsidy	0
2021, Medicare subsidy	0
2022-2026, Medicare subsidy	0
2017, Net payments	8
2018, Net payments	7
2019, Net payments	7
2020, Net payments	6
2021, Net payments	5
2022-2026, Net payments	$ 18

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 benefit payments retiree contributions in year one.

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

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Amount of benefits from a defined benefit plan expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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- Definition

Amount of the prescription drug subsidy receipts to be received after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

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Amount of the prescription drug subsidy receipts to be received in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of the prescription drug subsidy receipts to be received in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of the prescription drug subsidy receipts to be received in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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