Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Convertible Senior Notes Due 2022	Convertible Senior Notes Due 2024	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Convertible Senior Notes Due 2022	Additional Paid-in Capital Convertible Senior Notes Due 2024	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2016	$ 42,352			$ 27	$ 132,246			$ (89,618)	$ (303)
Beginning Balance, shares at Dec. 31, 2016				27,150,674
Stock-based compensation	9,299				9,299
Issuance of common stock in offering, net of issuance costs	9,870			$ 1	9,869
Issuance of common stock in offering, net of issuance costs, shares				553,825
Purchase of convertible note capped call hedge		$ (12,922)				$ (12,922)
Equity component of convertible notes		22,094				22,094
Exercise of stock options	2,869				2,869
Exercise of stock options, shares				497,175
Issuance of shares under employee stock purchase plan	1,540				1,540
Issuance of shares under employee stock purchase plan, shares				128,786
Other comprehensive income (loss)	523								523
Net loss	(19,634)							(19,634)
Balance at Dec. 31, 2017	55,991			$ 28	164,995			(109,252)	220
Ending Balance, shares at Dec. 31, 2017				28,330,460
Cumulative effect of adoption of ASU 2014-09, net of taxes	9,097							9,097
Stock-based compensation	25,825				25,825
Vesting of restricted stock units	1			$ 1
Vesting of restricted stock units, shares				671,412
Restricted stock units withheld to settle employee tax withholding liability	(7,925)				(7,925)
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
Stock-based compensation	33,989				33,989
Issuance of common stock in offering, net of issuance costs	138,834			$ 3	138,831
Issuance of common stock in offering, net of issuance costs, shares				2,645,000
Issuance of common stock in connection with the acquisition of NC4	32,798				32,798
Issuance of common stock in connection with acquisition, shares				320,998
Vesting of restricted stock units, shares				275,680
Restricted stock units withheld to settle employee tax withholding liability	(4,602)				(4,602)
Restricted stock units withheld to settle employee tax withholding liability, shares				(54,312)
Purchase of convertible note capped call hedge			$ (44,948)				$ (44,948)
Equity component of convertible notes			$ 86,133				$ 86,133
Exercise of stock options	$ 17,411			$ 1	17,410
Exercise of stock options, shares	918,588			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 repurchased convertible notes		(36,649)				(36,649)
Termination of capped call hedge for the convertible notes		$ 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