Cash, Cash Equivalents, and Investments - Summary of Amortized Cost and Fair Value of Short-term and Long-term Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Due in less than one year	$ 49,711	$ 50,254
Due after one year, through two years	4,594	$ 8,525
Amortized Cost
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Due in less than one year	49,711
Due after one year, through two years	4,594
Due after two years	0
Total short-term and long-term investments	54,305
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Due in less than one year	49,709
Due after one year, through two years	4,598
Due after two years	0
Total short-term and long-term investments	$ 54,307