Business and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands		9 Months Ended
	Oct. 09, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) Segment	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Cash, cash equivalents and investments		$ 111,400
Cash and cash equivalents		55,819	$ 73,551	$ 52,299	$ 256,965
Short-term investments		44,090	136,793
Restricted cash and investments		$ 11,478	$ 782
Number of operating segments | Segment		1
Subsequent Event
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common stock issued | shares	3,250,000
Common stock price per share | $ / shares	$ 39.00
Period granted to underwriters to purchase of additional shares	30 days
Common stock available for sale | shares	487,500
Net proceeds from issue of common stock	$ 120,000