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.

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- Definition

Description of investment policy and strategy for defined benefit plan asset. Includes, but is not limited to, investment allocation decision and factor pertinent to understanding investment policy and strategy for plan asset. Factor includes, but is not limited to, investment goal, risk management practice, permitted and prohibited investment including use of derivative, diversification, and relationship between plan asset and obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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- Definition

Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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Postretirement Benefit Plans - Asset Allocation Range (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
U.S. equities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	18.00%	22.00%
International equities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	9.00%	8.00%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	72.00%	68.00%
Cash and other
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	1.00%	2.00%
Minimum [Member] \| U.S. equities
Defined Benefit Plan Disclosure [Line Items]
Asset Allocation Range	0
Minimum [Member] \| International equities
Defined Benefit Plan Disclosure [Line Items]
Asset Allocation Range	0
Minimum [Member] \| Fixed income
Defined Benefit Plan Disclosure [Line Items]
Asset Allocation Range	0.5
Minimum [Member] \| Cash and other
Defined Benefit Plan Disclosure [Line Items]
Asset Allocation Range	0.00
Maximum [Member] \| U.S. equities
Defined Benefit Plan Disclosure [Line Items]
Asset Allocation Range	0.5
Maximum [Member] \| International equities
Defined Benefit Plan Disclosure [Line Items]
Asset Allocation Range	0.25
Maximum [Member] \| Fixed income
Defined Benefit Plan Disclosure [Line Items]
Asset Allocation Range	1
Maximum [Member] \| Cash and other
Defined Benefit Plan Disclosure [Line Items]
Asset Allocation Range	0.1