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Acquisitions - Summary of Purchase Price Allocation (Parenthetical) (Detail) - Power Service [Member] $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Business Acquisition [Line Items]
Goodwill	$ 116
Trade Names [Member]
Business Acquisition [Line Items]
Estimated useful lives	20 years
Customer Relationships [Member]
Business Acquisition [Line Items]
Estimated useful lives	10 years

X

- 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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- Definition

The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

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- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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