Unaudited Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated other comprehensive income	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)
Realized and unrealized income on derivative instruments	2,935			2,935
Unrealized gains (losses) 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, 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]
Realized and unrealized income on derivative instruments	3,847
Unrealized gains (losses) on available for sale securities	44
Net loss	(47,127)
Balance at Jun. 30, 2019	100,194	$ 30	285,001	258	(185,095)
Ending (in shares) at Jun. 30, 2019		30,327,027
Balance (in shares) at Mar. 31, 2019		30,263,237
Balance at Mar. 31, 2019	109,995	$ 30	271,260	(688)	(160,607)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	14,796		14,796
Common stock issued under employee stock plans, net (in shares)		63,790
Common stock issued under employee stock plans, net	(1,055)	$ 0	(1,055)
Realized and unrealized income on derivative instruments	912			912
Unrealized gains (losses) on available for sale securities	34			34
Net loss	(24,488)				(24,488)
Balance at Jun. 30, 2019	100,194	$ 30	285,001	258	(185,095)
Ending (in shares) at Jun. 30, 2019		30,327,027
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
Realized and unrealized income on derivative instruments	545			545
Unrealized gains (losses) 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
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]
Realized and unrealized income on derivative instruments	3,912
Unrealized gains (losses) on available for sale securities	74
Net loss	(55,753)
Balance at Jun. 30, 2020	78,530	$ 32	347,447	3,536	(272,485)
Ending (in shares) at Jun. 30, 2020		31,543,519
Balance (in shares) at Mar. 31, 2020		31,466,270
Balance at Mar. 31, 2020	80,041	$ 31	327,881	291	(248,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	17,623		17,623
Common stock issued under employee stock plans, net (in shares)		77,249
Common stock issued under employee stock plans, net	498	$ 1	497
Realized and unrealized income on derivative instruments	3,367			3,367
Unrealized gains (losses) on available for sale securities	(122)			(122)
Purchase of capped calls related to Convertible senior notes	(29,348)		(29,348)
Equity component of Convertible senior notes, net	30,794		30,794
Net loss	(24,323)				(24,323)
Balance at Jun. 30, 2020	$ 78,530	$ 32	$ 347,447	$ 3,536	$ (272,485)
Ending (in shares) at Jun. 30, 2020		31,543,519