Benefit Plans (Schedule of estimated amounts to be recognized from Accumulated other comprehensive income into net periodic cost (benefit) during next fiscal year) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service credit	$ 0
Amortization of net actuarial loss	36
Total estimated amounts to be recognized	36
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service credit	(2)
Amortization of net actuarial loss	0
Total estimated amounts to be recognized	$ (2)

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.

No definition available.

+ Details

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (s)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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- Definition

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.

+ References

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- Definition

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.

+ References

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- Details

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- Details

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