Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2016	41,303,363
Balance at Dec. 31, 2016	$ 41	$ 459,928	$ 1,976	$ 579	$ 462,524
Issuance of common stock from exercise of stock options (in shares)	300,982
Issuance of common stock from exercise of stock options	$ 1	2,174	0	0	2,175
Issuance of common stock from restricted stock unit grants, net of shares withheld for tax (in shares)	1,004,785
Issuance of common stock from restricted stock unit grants, net of shares withheld for tax	$ 1		0	0
Issuance of common stock from restricted stock unit grants, net of shares withheld for tax		(27,776)			$ (27,775)
Issuance of common stock from employee stock purchase plan (in shares)	171,099				171,099
Issuance of common stock from employee stock purchase plan	$ 0	5,776	0	0	$ 5,776
Stock-based compensation expense	0	44,832	0	0	44,832
Cumulative effect of change in accounting principle	0	0	(1,217)	0	(1,217)
Net loss	0	0	(74,904)	0	(74,904)
Other comprehensive loss, net	$ 0	0	0	(10)	(10)
Balance (in shares) at Dec. 31, 2017	42,780,229
Balance at Dec. 31, 2017	$ 43	484,934	(74,145)	569	411,401
Issuance of common stock from exercise of stock options (in shares)	187,742
Issuance of common stock from exercise of stock options	$ 0	719	0	0	719
Issuance of common stock from restricted stock unit grants, net of shares withheld for tax (in shares)	1,041,258
Issuance of common stock from restricted stock unit grants, net of shares withheld for tax	$ 1		0	0
Issuance of common stock from restricted stock unit grants, net of shares withheld for tax		(19,286)			$ (19,285)
Issuance of common stock from employee stock purchase plan (in shares)	283,493				283,493
Issuance of common stock from employee stock purchase plan	$ 0	5,906	0	0	$ 5,906
Stock-based compensation expense	0	63,884	0	0	63,884
Net loss	0	0	(95,751)	0	(95,751)
Other comprehensive loss, net	$ 0	0	0	(180)	(180)
Balance (in shares) at Dec. 31, 2018	44,292,722
Balance at Dec. 31, 2018	$ 44	536,157	(169,896)	389	$ 366,694
Issuance of common stock from exercise of stock options (in shares)	253,980				253,980
Issuance of common stock from exercise of stock options	$ 0	2,616	0	0	$ 2,616
Issuance of common stock from restricted stock unit grants, net of shares withheld for tax (in shares)	1,154,043
Issuance of common stock from restricted stock unit grants, net of shares withheld for tax	$ 2		0	0
Issuance of common stock from restricted stock unit grants, net of shares withheld for tax		(34,140)			$ (34,138)
Issuance of common stock from employee stock purchase plan (in shares)	208,721				208,721
Issuance of common stock from employee stock purchase plan	$ 0	6,374	0	0	$ 6,374
Stock-based compensation expense	0	76,855	0	0	76,855
Net loss	0	0	(72,911)	0	(72,911)
Other comprehensive loss, net	$ 0	0	0	1,111	1,111
Balance (in shares) at Dec. 31, 2019	45,909,466
Balance at Dec. 31, 2019	$ 46	$ 587,862	$ (242,807)	$ 1,500	$ 346,601