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Description of Business and Basis of Presentation - Additional Information (Detail)		6 Months Ended
	Mar. 01, 2017	Jun. 30, 2017
Description Of Business And Basis Of Presentation [Line Items]
Number of Reportable Segments		2
HST & WHC & MPLXT [Member]
Description Of Business And Basis Of Presentation [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 01, 2017

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Description Of Business And Basis Of Presentation [Line Items]

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e845-128460

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-Name Accounting Standards Codification
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-Topic 805
-SubTopic 10
-Section 50
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