Summary of Company Cash, Cash Equivalents and Short-term Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	$ 123,214	$ 192,602
Cash, cash equivalents and short-term investments, Gross unrealized gains	1
Cash, cash equivalents and short-term investments, Gross unrealized losses		(111)
Cash, cash equivalents and short-term investments, Fair market value	123,215	192,491
Cash and Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	111,819	75,304
Cash, cash equivalents and short-term investments, Fair market value	111,819	75,304
Commercial Paper [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	4,998	48,936
Cash, cash equivalents and short-term investments, Gross unrealized losses		(37)
Cash, cash equivalents and short-term investments, Fair market value	4,998	48,899
Government and Government Agency Bonds [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	3,067	50,966
Cash, cash equivalents and short-term investments, Gross unrealized gains	1
Cash, cash equivalents and short-term investments, Gross unrealized losses		(48)
Cash, cash equivalents and short-term investments, Fair market value	3,068	50,918
Corporate Bonds [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	3,330	17,396
Cash, cash equivalents and short-term investments, Gross unrealized losses		(26)
Cash, cash equivalents and short-term investments, Fair market value	3,330	17,370
Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	111,819	80,304
Cash, cash equivalents and short-term investments, Fair market value	111,819	80,304
Short-term Investments [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents and short-term investments, Amortized cost	11,395	112,298
Cash, cash equivalents and short-term investments, Gross unrealized gains	1
Cash, cash equivalents and short-term investments, Gross unrealized losses		(111)
Cash, cash equivalents and short-term investments, Fair market value	$ 11,396	$ 112,187