Cash, Cash Equivalents, and Investments - Summary of Amortized Cost and Fair Value of Short-term and Long-term Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Due in less than one year	$ 29,630	$ 48,415
Due after one year, through two years	0	$ 234
Amortized Cost
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Due in less than one year	29,630
Due after one year, through two years	0
Due after two years	0
Total short-term and long-term investments	29,630
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Due in less than one year	29,603
Due after one year, through two years	0
Due after two years	0
Total short-term and long-term investments	$ 29,603