Investments (Tables)

12 Months Ended

Dec. 31, 2019

Investments

Schedule of amortized cost and fair value of available-for-sale securities

			Gross		Gross
	Amortized		Unrealized		Unrealized		Estimated
	Cost		Gains		Losses		Fair Value
	(in thousands)
December 31, 2019
U.S. treasuries	$	105,096	$	38	$	(4)	$	105,130
Government agency securities		1,139		—		—		1,139
Corporate debt		6,003		—		(1)		6,002
Commercial paper		2,981		—		—		2,981
Total	$	115,219	$	38	$	(5)	$	115,252
December 31, 2018
U.S. treasuries	$	37,191	$	—	$	(7)	$	37,184
Corporate debt		8,525		—		(9)		8,516
Commercial paper		2,489		—		—		2,489
Total	$	48,205	$	—	$	(16)	$	48,189

Schedule of fair value and unrealized losses of available-for-sale securities in a loss position

	December 31, 2019				December 31, 2018
			Gross				Gross
	Estimated		Unrealized		Estimated		Unrealized
	Fair Value		Losses		Fair Value		Losses
		(in thousands)
U.S. treasuries	$	22,943	$	(4)	$	37,184	$	(7)
Corporate debt		6,002		(1)		8,516		(9)
Total	$	28,945	$	(5)	$	45,700	$	(16)