Financial instruments (Tables)

9 Months Ended

Sep. 30, 2018

Investments, All Other Investments [Abstract]

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

The Company has no short-term investments as of September 30, 2018. The Company’s short-term investments as at December 31, 2017, consisted of available-for-sale securities as follows:

(in thousands) December 31, 2017	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Short-term investments:
U.S. treasury securities	$	56,123	$	—	$	(70	)	$	56,053
Contractual maturities:
Due within one year	$	56,123						$	56,053

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
(in thousands) December 31, 2017	Fair value		Gross unrealized losses			Fair value		Gross unrealized losses
U.S. treasury securities	$	15,983	$	(27	)	$	40,070	$	(43	)

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

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

(in thousands)	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, 2017
Short-term investments – U.S. treasury securities	$	56,053	$	—	$	—	$	56,053
	$	56,053	$	—	$	—	$	56,053