Description of Business and Significant Accounting Policies - Additional Information (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Increase to opening retained earnings	$ 139
ASU No. 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Increase to opening retained earnings	$ 139

Amount of the cumulative effect on retained earnings net of related income tax effect.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22663-107794

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