Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value of Financial Assets

Financial assets subject to fair value measurements on a recurring basis and the level of inputs used in such measurements are as follows:

	December 31, 2016
	Fair Value Measurements Using
	Total		Level 1		Level 2		Level 3
	(in thousands)
Money market funds	$	26,439	$	26,439	$	—	$	—
Commercial paper		29,428		—		29,428		—
Corporate securities		19,578		—		19,578		—
Agency discount instruments		2,998		—		2,998		—
U.S. government agency securities		22,015		—		22,015		—
Total financial assets	$	100,458	$	26,439	$	74,019	$	—

	December 31, 2015
	Fair Value Measurements Using
	Total		Level 1		Level 2		Level 3
	(in thousands)
Money market funds	$	19,787	$	19,787	$	—	$	—
Commercial paper		3,996		—		3,996		—
Corporate debt securities		16,540		—		16,540		—
U.S. government agency securities		4,014		—		4,014		—
Total financial assets	$	44,337	$	19,787	$	24,550	$	—

Fair Value of Financial Liabilities

The following tables set forth the fair value of the Company’s financial liabilities as of December 31, 2016 and 2015:

	December 31, 2016
	Fair Value Measurements Using
	Total		Level 1		Level 2		Level 3
	(in thousands)
Contingent acquisition consideration payable	$	4,380	$	—	$	—	$	4,380
Asset retirement obligation		709		—		—		709
Total financial liabilities	$	5,089	$	—	$	—	$	5,089

	December 31, 2015
	Fair Value Measurements Using
	Total		Level 1		Level 2		Level 3
	(in thousands)
Contingent acquisition consideration payable	$	4,278	$	—	$	—	$	4,278
Asset retirement obligation		136		—		—		136
Total financial liabilities	$	4,414	$	—	$	—	$	4,414

Summary of Contingent Acquisition Consideration Payable Recorded as Non-Current Liabilities in Accompanying Consolidated Balance Sheets

The following is a summary of the contingent acquisition consideration payable, recorded as a non-current liability in the accompanying consolidated balance sheets:

	Amount
	(in thousands)
Balance, December 31, 2015	$	4,278
Change in fair value of contingent acquisition    consideration payable		102
Balance, December 31, 2016	$	4,380

Asset Retirement Obligation Included in Facilities Lease Obligations in Accompanying Consolidated Balance Sheets

The asset retirement obligation is included in facilities lease obligations in the accompanying consolidated balance sheets.

	Amount
	(in thousands)
Balance, December 31, 2015	$	136
Asset retirement obligation accretion expense		106
Addition of asset retirement obligation payable		467
Balance, December 31, 2016	$	709