Share-Based Compensation - Weighted Average Grant Date Fair Value of Options Granted and Total Intrinsic Value of Options Exercised (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted average grant date fair value per share	$ 6.53	$ 6.53
Total intrinsic value of options exercised	$ 1,463	$ 3,815

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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)(2)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration