Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis

Assets and liabilities measured at fair value on a recurring basis are as follows (in thousands):

			Fair Value Measurements Using
			QuotedPricesin ActiveMarkets forIdentical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of December 31, 2015:
Assets:
Current:
Cash and cash equivalents	$	53,025	$	53,025	$	—	$	—
Short-term investments:
Commercial paper		2,996		—		2,996		—
Corporate debt securities		39,514		—		39,514		—
Sub-total short-term investments		42,510		—		42,510		—
Long-term investments:
United States Treasury securities		1,999		1,999		—		—
Asset-backed securities		10,912		—		10,912		—
Corporate debt securities		16,903		—		16,903		—
Sub-total long-term investments		29,814		1,999		27,815		—
Total assets measured at fair value	$	125,349	$	55,024	$	70,325	$	—
As of December 31, 2014:
Assets:
Cash and cash equivalents	$	13,899	$	13,899	$	—	$	—
Short-term investments - Corporate debt securities		1,954		—		1,954		—
Total assets measured at fair value	$	15,853	$	13,899	$	1,954	$	—
Liabilities:
Preferred stock warrant liabilities	$	319	$	—	$	—	$	319

Schedule of Available-for-sale Investments

As of December 31, 2015 and 2014, available-for-sale investments are detailed as follows (in thousands):

	December 31, 2015
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Market Value
Short-term investments:
Commercial paper	$	2,996	$	—	$	—		$	2,996
Corporate debt securities		39,575		—		(61	)		39,514
	$	42,571	$	—	$	(61	)	$	42,510
Long-term investments:
United States Treasury securities	$	2,006	$	—	$	(7	)	$	1,999
Asset-backed securities		10,928		—		(16	)		10,912
Corporate debt securities		16,990		—		(87	)		16,903
	$	29,924	$	—	$	(110	)	$	29,814

	December 31, 2014
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Market Value
Short-term:
Corporate debt securities	$	1,954	$	—	$	—	$	1,954

Schedule of Available-for-sale Investments in Unrealized Loss Position

Available-for-sale investments that are in an unrealized loss position as of December 31, 2015 are as follows (in thousands):

	Estimated Fair Value		Gross Unrealized Losses
United States Treasury securities	$	1,999	$	(7	)
Asset-backed securities		10,912		(16	)
Corporate debt securities		56,416		(148	)
	$	69,327	$	(171	)

Schedule of Reconciliation of All Liabilities Measured at Fair Value Using Level 3 Significant Unobservable Inputs

The following table provides a reconciliation of all liabilities measured at fair value using Level 3 significant unobservable inputs (in thousands):

	Warrant Liabilities
Balance as of December 31, 2014	$	319
Change in fair value		(29	)
Balance as of May 5, 2015	$	290
Reclassification to additional paid-in capital as of IPO on    May 6, 2015		(290	)
Balance as of December 31, 2015	$	—