Unaudited Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Balance (in shares) at Dec. 31, 2018		29,576,880
Balance at Dec. 31, 2018	$ 125,370	$ 30	$ 266,941	$ (3,633)	$ (137,968)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	8,961		8,961
Common stock issued under employee stock plans, net (in shares)		686,357
Common stock issued under employee stock plans, net	(4,642)	$ 0	(4,642)
Unrealized gains on derivative instruments	2,935			2,935
Unrealized gains on available for sale securities	10			10
Net loss	(22,639)				(22,639)
Balance at Mar. 31, 2019	109,995	$ 30	271,260	(688)	(160,607)
Ending (in shares) at Mar. 31, 2019		30,263,237
Balance (in shares) at Dec. 31, 2019		30,583,311
Balance at Dec. 31, 2019	93,532	$ 31	310,682	(449)	(216,732)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	12,883		12,883
Common stock issued under employee stock plans, net (in shares)		882,959
Common stock issued under employee stock plans, net	4,316	$ 0	4,316
Unrealized gains on derivative instruments	545			545
Unrealized gains on available for sale securities	195			195
Net loss	(31,430)				(31,430)
Balance at Mar. 31, 2020	$ 80,041	$ 31	$ 327,881	$ 291	$ (248,162)
Ending (in shares) at Mar. 31, 2020		31,466,270