Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Fair Value Measurement

The following tables represent the financial instruments measured at fair value on a recurring basis on the financial statements of the Company and the valuation approach applied to each class of financial instruments at December 31, 2017 and 2016 (see Note 2, Summary of Significant Accounting Policies for further information):

	December 31, 2017
	(in thousands)
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
Cash and cash equivalents:
Money market funds	$	7,832	$	—	$	—	$	7,832
Investments:
Certificates of deposit	—		13,441		—		13,441
US Treasury securities	14,716		—		—		14,716
US Agency securities	—		8,459		—		8,459
Commercial paper	—		9,171		—		9,171
Asset-backed securities	—		3,025		—		3,025
Corporate notes and bonds	—		31,836		—		31,836
Total investments	14,716		65,932		—		80,648
Total assets measured at fair value	$	22,548	$	65,932	$	—	$	88,480

	December 31, 2016
	(in thousands)
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
Cash and cash equivalents:
Money market funds	$	10,970	$	—	$	—	$	10,970
Investments:
Certificates of deposit	—		7,257		—		7,257
US Treasury securities	8,544		—		—		8,544
US Agency securities	—		4,501		—		4,501
Asset-backed securities	—		5,557		—		5,557
Corporate notes and bonds	—		32,660		—		32,660
Total investments	8,544		49,975		—		58,519
Total assets measured at fair value	$	19,514	$	49,975	$	—	$	69,489