Financial instruments (Tables)

12 Months Ended

Dec. 31, 2016

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


December 31, 2016	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Short-term investments:
U.S. treasury securities	$	70,819	$	—	$	(61	)	$	70,758

Long-term investments:
U.S. treasury securities	$	50,155	$	—	$	(109	)	$	50,046

Contractual maturities:
Due within one year	$	70,819						$	70,758
Due after one year through two years		50,155							50,046

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. treasury 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
December 31, 2016
U.S. treasury securities	$	120,804	$	(170	)		N/A		N/A

December 31, 2015
U.S. treasury securities	$	71,411	$	(290	)		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—December 31, 2016
Short-term investments—U.S. treasury securities	$	70,758	$	—	$	—		$	70,758
Long-term investments—U.S. treasury securities		50,046		—		—			50,046

	$	120,804	$	—	$	—		$	120,804

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):


	BANK LOAN WARRANT DERIVATIVE LIABILITIES
BALANCES—December 31, 2014	$	72
Change in fair value of derivative liability		52

BALANCES—December 31, 2015		124
Change in fair value of derivative liability		(81	)
Exercise of warrants		(43	)

BALANCES—December 31, 2016	$	—