Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate, Interest Rate

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Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Under Historical Estimation Methods, Interest Rate

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Defined Benefit Plan, Interest Cost, Assumption Change

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Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlements, Net of Tax

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Defined Benefit Plans, Increase (Decrease) in Stockholder's Equity

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
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Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.

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Amount included in accumulated other comprehensive (income) loss for prior service cost (credit) expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after tax, of increase (decrease) to other comprehensive income from settlement and curtailment gain (loss) of defined benefit plan.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Employee Benefit Plans - Components of Net Periodic Benefit Cost (Benefit) and Other Amounts Recognized in Other Comprehensive Income (Loss), Additional Information (Details) - USD ($)		1 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2017	Sep. 30, 2017	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions					$ 280,000,000
Reduction in interest cost component of net periodic interest					32
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pre-tax settlement charge					750,000,000
After-tax settlement charge	$ 750,000,000				488,000,000
Reduction to stockholder's equity					144,000,000
Employer contributions					280,000,000	$ 301,000,000
Increase to unrecognized net loss from pension settlement transaction					750,000,000
Estimated net gain (loss) for the defined benefit plans			$ 48,000,000		$ 48,000,000
Pension Benefits \| Qualified Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions		$ 280,000,000
Discount rate used to measure interest cost			3.37%	3.58%
Discount rate used to measure interest cost, historical method			3.92%	4.22%
Pension Benefits \| Non-Qualified Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate used to measure interest cost					3.55%
Discount rate used to measure interest cost, historical method			4.19%
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pre-tax settlement charge						0
Employer contributions					$ 0	$ 0
Discount rate used to measure interest cost					3.13%
Discount rate used to measure interest cost, historical method					3.97%
Estimated net gain (loss) for the defined benefit plans			$ 6,000,000		$ 6,000,000
Estimated prior service cost for the other postretirement benefit plans			$ (7,000,000)		$ (7,000,000)