Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

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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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Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Oct. 02, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2018
Business Acquisition [Line Items]
Total consideration, net		$ 8,842	$ 3,700	$ 10,000
Goodwill		910,088	$ 902,579	$ 901,928	$ 906,766
Business Acquisition, Intangible Assets		$ 4,538
PCP Oil Tools S.A. and Ener Tools S.A. ("PCP") [Member]
Business Acquisition [Line Items]
Business Acquisition	Oct. 02, 2017
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Total consideration, net	$ 8,842
Goodwill	5,053
Business Acquisition, Intangible Assets	$ 4,538
Finite-Lived Intangible Assets, Remaining Amortization Period	9 years