Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect of Adoption of Net of Taxes	Convertible Senior Notes Due 2024	Convertible Senior Notes Due 2022	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Convertible Senior Notes Due 2024	Additional Paid-in Capital Convertible Senior Notes Due 2022	Accumulated Deficit	Accumulated Deficit Cumulative Effect of Adoption of Net of Taxes	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2017	$ 55,991	$ 9,097			$ 28	$ 164,995			$ (109,252)	$ 9,097	$ 220
Beginning Balance, shares at Dec. 31, 2017					28,330,460
Accounting Standards Update Extensible List	us-gaap:AccountingStandardsUpdate201409Member								us-gaap:AccountingStandardsUpdate201409Member
Stock-based compensation	$ 25,825					25,825
Vesting of restricted stock units and performance-based restricted stock units	1				$ 1
Vesting of restricted stock units and performance-based restricted stock units, shares					671,412
Restricted stock units and performance-based restricted stock units withheld to settle employee tax withholding liability	(7,925)					(7,925)
Restricted stock units and performance-based restricted stock units withheld to settle employee tax withholding liability, shares					(154,567)
Exercise of stock options	10,149				$ 1	10,148
Exercise of stock options, shares					778,370
Issuance of shares under employee stock purchase plan	1,823					1,823
Issuance of shares under employee stock purchase plan, shares					74,517
Other comprehensive income (loss)	(5,288)										(5,288)
Net loss	(47,515)								$ (47,515)
Balance at Dec. 31, 2018	42,158				$ 30	194,866			(147,670)		(5,068)
Ending Balance, shares at Dec. 31, 2018					29,700,192
Issuance of common stock, net of cost	138,834				$ 3	138,831
Issuance of common stock, net of cost, shares					2,645,000
Issuance of common stock in connection with acquisition	32,798					32,798
Issuance of common stock in connection with acquisition, shares					320,998
Stock-based compensation	33,989					33,989
Vesting of restricted stock units and performance-based restricted stock units, shares					275,680
Restricted stock units and performance-based restricted stock units withheld to settle employee tax withholding liability	(4,602)					(4,602)
Restricted stock units and performance-based restricted stock units withheld to settle employee tax withholding liability, shares					(54,312)
Exercise of stock options	17,411				$ 1	17,410
Exercise of stock options, shares					918,588
Issuance of shares under employee stock purchase plan	2,337					2,337
Issuance of shares under employee stock purchase plan, shares					42,481
Equity component of the convertible notes due 2024, net of allocated issuance costs and taxes			$ 86,133				$ 86,133
Purchase of capped call hedge for the convertible notes due2024, including issuance costs			$ (44,948)				$ (44,948)
Equity component of repurchased convertible notes due 2022				$ (36,649)				$ (36,649)
Termination of capped call hedge for the convertible notes due 2022				$ 5,780				$ 5,780
Other comprehensive income (loss)	(679)										(679)
Net loss	(52,250)								(52,250)
Balance at Dec. 31, 2019	220,312				$ 34	425,945			(199,920)		(5,747)
Ending Balance, shares at Dec. 31, 2019					33,848,627
Issuance of common stock in connection with acquisition	53,193					53,193
Issuance of common stock in connection with acquisition, shares					462,224
Stock-based compensation	47,079					47,079
Vesting of restricted stock units and performance-based restricted stock units, shares					451,879
Restricted stock units and performance-based restricted stock units withheld to settle employee tax withholding liability	(6,364)					(6,364)
Restricted stock units and performance-based restricted stock units withheld to settle employee tax withholding liability, shares					(48,469)
Exercise of stock options	$ 8,160				$ 1	8,159
Exercise of stock options, shares	323,838				323,838
Issuance of shares under employee stock purchase plan	$ 3,389					3,389
Issuance of shares under employee stock purchase plan, shares					49,319
Settlement of convertible notes due 2022	11,375					11,375
Settlement of convertible notes due 2022, shares					362,029
Other comprehensive income (loss)	8,557										8,557
Net loss	(93,396)								(93,396)
Balance at Dec. 31, 2020	$ 252,305				$ 35	$ 542,776			$ (293,316)		$ 2,810
Ending Balance, shares at Dec. 31, 2020					35,449,447