Cash Proceeds Along with Fair Value Disclosures Related to Grants, Exercises, and Vested Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-average fair value of options granted during period	$ 1.05	$ 0.67
Total fair value of shares vested during the period	$ 334	$ 708

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration