Financial instruments (Tables)

3 Months Ended

Mar. 31, 2016

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


March 31, 2016	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Short-term investments:
U.S. treasury securities	$	33,033	$	2	$	(11	)	$	33,024

Long-term investments:
U.S. treasury securities	$	38,661	$	—	$	(38	)	$	38,623

Contractual maturities:
Due within one year	$	33,033						$	33,024
Due after one year through two years		38,661							38,623

December 31, 2015	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Short-term investments:
U.S. treasury securities	$	33,014	$	—	$	(61	)	$	32,953
U.S. government agency securities		2,003		—		—			2,003

	$	35,017	$	—	$	(61	)	$	34,956

Long-term investments:
U.S. government agency securities	$	38,687	$	—	$	(229	)	$	38,458

Contractual maturities:
Due within one year	$	35,017						$	34,956
Due after one year through two years		38,687							38,458

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
March 31, 2016
U.S. treasury securities	$	60,630	$	(49	)		N/A		N/A
December 31, 2015
U.S. treasury securities	$	32,953	$	(61	)		N/A		N/A
U.S. Government agency securities		38,458		(229	)		N/A		N/A

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 – March 31, 2016
Short-term investments – U.S. treasury securities	$	33,024	$	—	$	—		$	33,024
Long-term investments – U.S. treasury securities		38,623		—		—			38,623
Bank loan warrant derivative liabilities		—		—		(74	)		(74	)

	$	71,647	$	—	$	(74	)	$	71,573

BALANCES – December 31, 2015
Short-term investments – U.S. treasury securities	$	32,953	$	—	$	—		$	32,953
Short-term investments – U.S. government agency securities		2,003		—		—			2,003
Long-term investments – U.S. treasury securities		38,458		—		—			38,458

Bank loan warrant derivative liabilities		—		—		(124	)		(124	)

	$	73,414	$	—	$	(124	)	$	73,290

Fair value of significant unobservable inputs (Level 3):


Three months ended March 31, 2016:	BANK LOAN WARRANT DERIVATIVE LIABILITIES
BALANCES – December 31, 2015	$	124
Change in fair value of derivative liabilities		(50	)

BALANCES – March 31, 2016	$	74