The amount of gains or losses recognized in net periodic benefit cost.

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- Definition

The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

+ 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 (h)(1)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Prior Service Cost
-URI http://asc.fasb.org/extlink&oid=49177896

+ Details

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- Definition

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.

+ References

No definition available.

+ Details

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Pension and Other Postretirement Benefits - Schedule of Amounts Expected to be Recognized in Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss recognition		$ 380	$ 468	$ 391
Prior service cost (benefit) recognition		13	16	18
Pension Benefits [Member] \| Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss recognition	$ 380
Prior service cost (benefit) recognition	13
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss recognition		24	17	13
Prior service cost (benefit) recognition		$ (24)	$ (37)	$ (25)
Other Postretirement Benefits [Member] \| Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss recognition	24
Prior service cost (benefit) recognition	$ (24)