Financial instruments (Tables)

9 Months Ended

Sep. 30, 2015

Investments, All Other Investments [Abstract]

Summary of Short-Term Investments and Long-Term Investments of Available-for-Sale Securities

The Company’s short-term investments and long-term investments are consisted of available-for-sale securities as follows:

September 30, 2015 Short-term investments:	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
U.S. treasury securities	$	6,034	$	2	$	—	$	6,036
U.S. government agency securities		2,001		1		—		2,002
	$	8,035	$	3	$	—	$	8,038
Contractual maturities:
Due within one year	$	8,035					$	8,038

The Company had no long-term investments consisting of available-for-sale securities on September 30, 2015.

December 31, 2014 Short-term investments:	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
U.S. treasury securities	$	12,199	$	—	$	(5	)	$	12,194
U.S. government agency securities		11,996		1		—			11,997
	$	24,195	$	1	$	(5	)	$	24,191
Long-term investments:
U.S. government agency securities	$	2,003	$	0	$	—		$	2,003
Contractual maturities:
Due within one year	$	24,195						$	24,191
Due after one year through two years		2,003							2,003

Aggregate Estimated Fair Value of Investments with Unrealized Losses

The aggregate estimated fair value of the Company’s investments with unrealized losses are as follows:

	Period of continuous unrealized loss
	12 months or less					Greater than 12 months
December 31, 2014	Fair value		Gross unrealized losses			Fair value	Gross unrealized losses
U.S. treasury securities	$	12,194	$	(5	)	NA	NA
September 30, 2015		NA		NA		NA	NA

Fair Value of Financial Instruments Measured At Fair Value on a Recurring Basis

The following tables present the fair value of our financial instruments that are measured at fair value on a recurring basis:

	QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT UN- OBSERVABLE INPUTS (LEVEL 3)			TOTAL
BALANCES – September 30, 2015
Short-term investments – U.S. treasury securities	$	6,036	$	—	$	—		$	6,036
Short-term investments – U.S. government agency securities		2,002		—		—			2,002
Bank loan warrant derivative liabilities		—		—		(142	)		(142	)
	$	8,038	$	—	$	(142	)	$	7,896
BALANCES – December 31, 2014
Short-term investments – U.S. treasury securities	$	12,194	$	—	$	—		$	12,194
Short-term investments – U.S. government agency securities		11,997		—		—			11,997
Long-term investments – U.S. government agency securities		2,003		—		—			2,003
Bank loan warrant derivative liabilities		—		—		(72	)		(72	)
	$	26,194	$	—	$	(72	)	$	26,122

Fair Value of Significant Unobservable Inputs

Fair value of significant unobservable inputs (Level 3):

Three months ended September 30, 2015:	BANK LOAN WARRANT DERIVATIVE LIABILITIES
BALANCES – June 30, 2015	$	66
Change in fair value of derivative liabilities		76
BALANCES – September 30, 2015	$	142

Nine months ended September 30, 2015:	BANK LOAN WARRANT DERIVATIVE LIABILITIES
BALANCES – December 31, 2014	$	72
Change in fair value of derivative liabilities		70
BALANCES – September 30, 2015	$	142