Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Cash equivalents
Carrying Value	$ 5,563	$ 22,858
Short-term investments
Amortized Cost	81,291	97,093
Unrealized Gains	58	17
Unrealized Losses	(4)	(7)
Aggregate Fair Value	81,345	97,103
Long-term investments
Amortized Cost	1,278
Unrealized Gains	0
Unrealized Losses	0
Aggregate Fair Value	1,278	0
Total marketable securities, Amortized Cost	88,132	119,951
Total marketable securities, Unrealized Gains	58	17
Total marketable securities, Unrealized Losses	(4)	(7)
Total marketable securities, Aggregate Fair Value	88,186	119,961
Money market funds
Cash equivalents
Carrying Value	3,068	15,223
U.S. treasury securities
Cash equivalents
Carrying Value		1,000
Short-term investments
Amortized Cost	67,051	65,491
Unrealized Gains	34	2
Unrealized Losses	(2)	(4)
Aggregate Fair Value	67,083	65,489
Corporate bonds
Short-term investments
Amortized Cost	9,075	19,708
Unrealized Gains	24	15
Unrealized Losses	(2)	(3)
Aggregate Fair Value	9,097	19,720
Long-term investments
Amortized Cost	1,278
Unrealized Gains	0
Unrealized Losses	0
Aggregate Fair Value	1,278
Commercial paper
Cash equivalents
Carrying Value	2,495	6,635
Short-term investments
Amortized Cost	5,165	11,894
Unrealized Gains	0	0
Unrealized Losses	0	0
Aggregate Fair Value	$ 5,165	$ 11,894