Unaudited Condensed Consolidated Statements of Stockholders' Equity - USD ($)	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2017	42,780,229
Balance at Dec. 31, 2017	$ 43,000	$ 484,934,000	$ (74,145,000)	$ 569,000	$ 411,401,000
Issuance of common stock from exercise of stock options (in shares)	136,690
Issuance of common stock from exercise of stock options		291,000			291,000
Issuance of common stock from restricted stock unit grant, net of shares withheld for tax (in shares)	102,702
Issuance of common stock from restricted stock unit grant, net of shares withheld for tax		(1,922,000)			$ (1,922,000)
Issuance of common stock from employee stock purchase plan purchases (in shares)	177,771				177,771
Issuance of common stock from employee stock purchase plan purchases		3,703,000			$ 3,703,000
Stock-based compensation expense		14,553,000			14,553,000
Net income (loss)			(22,991,000)		(22,991,000)
Other comprehensive income, net				(275,000)	(275,000)
Balance (in shares) at Mar. 31, 2018	43,197,392
Balance at Mar. 31, 2018	$ 43,000	501,559,000	(97,136,000)	294,000	404,760,000
Balance (in shares) at Dec. 31, 2018	44,292,722
Balance at Dec. 31, 2018	$ 44,000	536,157,000	(169,896,000)	389,000	$ 366,694,000
Issuance of common stock from exercise of stock options (in shares)	78,205				78,205
Issuance of common stock from exercise of stock options		646,000			$ 646,000
Issuance of common stock from restricted stock unit grant, net of shares withheld for tax (in shares)	168,227
Issuance of common stock from restricted stock unit grant, net of shares withheld for tax	$ 1,000	(4,017,000)			$ (4,016,000)
Issuance of common stock from employee stock purchase plan purchases (in shares)	121,549				121,549
Issuance of common stock from employee stock purchase plan purchases		3,477			$ 3,477
Stock-based compensation expense		18,758,000			18,758,000
Net income (loss)			(22,745,000)		(22,745,000)
Other comprehensive income, net				540,000	540,000
Balance (in shares) at Mar. 31, 2019	44,660,703
Balance at Mar. 31, 2019	$ 45,000	$ 555,021,000	$ (192,641,000)	$ 929,000	$ 363,354,000