Short Term Investments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
Jun. 30, 2018	Mar. 31, 2018
Investments Schedule [Abstract]
Short term investments	$ 17,085	$ 16,000
Bank certificates of deposit interest bearing rate	2.50%
Bank certificates of deposit maturity month and year	2018-08

Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(4))
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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Name:	us-gaap_ShortTermInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant