Cash, Cash Equivalents, and Short-Term Investments - Schedule of Short-Term Investments at Fair Value and Length of Continuous Unrealized Loss Position (Detail) - Corporate Debt Obligations [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 73,673	$ 12,735
Less than 12 Months, Unrealized Losses	286	47
12 Months or Greater, Fair Value	10,609	12,088
12 Months or Greater, Unrealized Losses	14	6
Total, Fair Value	84,282	24,823
Total, Unrealized Losses	$ 300	$ 53