Financial instruments (Tables)

6 Months Ended

Jun. 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:

June 30, 2015	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
Short-term investments:
U.S. treasury securities	$	12,102	$	3	$	—	$	12,105
U.S. Government agency securities		2,003		1		—		2,004
	$	14,105	$	4	$	—	$	14,109
Contractual maturities:
Due within one year	$	14,105					$	14,109

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

December 31, 2014	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Short-term investments:
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
	Fair value		Gross unrealized losses			Fair value		Gross unrealized losses
December 31, 2014
U.S. treasury securities	$	12,194	$	(5	)		NA		NA
June 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 – June 30, 2015
Short-term investments – U.S. treasury securities	$	12,105	$	—	$	—		$	12,105
Short-term investments – U.S. government agency securities		2,004		—		—			2,004
Bank loan warrant derivative liabilities		—		—		(66	)		(66	)
	$	14,109	$	—	$	(66	)	$	14,043
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):

	BANK LOAN WARRANT DERIVATIVE LIABILITIES			TOTAL
Three months ended June 30, 2015:
BALANCES - March 31, 2015	$	79		$	79
Change in fair value of derivative liabilities		(13	)		(13	)
BALANCES – June 30, 2015	$	66		$	66

	BANK LOAN WARRANT DERIVATIVE LIABILITIES			TOTAL
Six months ended June 30, 2015:
BALANCES – December 31, 2014	$	72		$	72
Change in fair value of derivative liabilities		(6	)		(6	)
BALANCES – June 30, 2015	$	66		$	66