Fair Value Measurements and Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Financial Assets Measured and Recognized at Fair Value on Recurring Basis

The following table summarizes, for assets recorded at fair value on a recurring basis, the respective fair value and the classification by level of input within the fair value hierarchy as described above (in thousands):

			Quoted Prices		Significant Other		Significant
	Total		In Active Markets		Observable Inputs		Unobservable Inputs
	Carrying Value		(Level 1)		(Level 2)		(Level 3)
September 30, 2016
Assets:
Money market funds - cash equivalent	$	225,735	$	225,735	$	—	$	—
Total cash equivalents	$	225,735	$	225,735	$	—	$	—
Other noncurrent liability:
Financing arrangement	$	74	$	—	$	—	$	74
December 31, 2015
Assets:
Money market funds - cash equivalent	$	208,588	$	208,588	$	—	$	—
Certificates of deposit		1,680		—		1,680		—
U.S. treasury securities		15,042		—		15,042		—
U.S. government agency securities		21,010		—		21,010		—
Total cash equivalents and    marketable securities	$	246,320	$	208,588	$	37,732	$	—

Quantitative Information About Inputs and Valuation Methodologies Used for Fair Value Measurements

The following table presents quantitative information about the inputs and valuation methodologies used for the fair value measurements classified in Level 3 at the fair value hierarchy at September 30, 2016:

	Fair Value  at			Significant
	September 30, 2016		Valuation	Unobservable	Weighted Average
	(in thousands)		Methodology	Input	(range,if applicable)
Financing arrangement	$	74	Expected value approach	Milestone dates	2017 to 2023
				Discount rate		5.50	%
				Percent probability of milestone achievements	18.2% to 80.0%