CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (unaudited) - USD ($) $ in Thousands	Total		Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2018	$ 219,383		$ 1	$ 551,937	$ (287)	$ (332,268)
Beginning balance, Shares at Dec. 31, 2018			125,818,000
Cumulative-effect adjustment upon adoption (ASC 842) at Dec. 31, 2018	2,693					2,693
Common stock issued upon vesting of restricted stock units, net, Shares			1,780,000
Common stock issued upon stock option exercise	37,638			37,638
Common stock issued upon stock option exercise, Shares			2,957,000
Common stock issued in connection with acquisition	30,092			30,092
Common stock issued in connection with acquisition, shares			1,944,000
Common stock issued under employee stock purchase plan	2,662			2,662
Common stock issued under employee stock purchase plan, shares			261,000
Stock-based compensation expense	32,296			32,296
Comprehensive Income (loss)	788	[1]			788
Other	232			232
Other, Shares			16,000
Net loss	(36,255)					(36,255)
Ending balance at Jun. 30, 2019	289,529		$ 1	654,857	501	(365,830)
Ending balance, Shares at Jun. 30, 2019			132,776,000
Beginning Balance at Mar. 31, 2019	234,995		$ 1	582,652	(306)	(347,352)
Beginning balance, Shares at Mar. 31, 2019			128,060,000
Common stock issued upon vesting of restricted stock units, net, Shares			882,000
Common stock issued upon stock option exercise	23,219			23,219
Common stock issued upon stock option exercise, Shares			1,629,000
Common stock issued in connection with acquisition	30,092			30,092
Common stock issued in connection with acquisition, shares			1,944,000
Common stock issued under employee stock purchase plan	2,662			2,662
Common stock issued under employee stock purchase plan, shares			261,000
Stock-based compensation expense	16,232			16,232
Comprehensive Income (loss)	807	[1]			807
Net loss	(18,478)					(18,478)
Ending balance at Jun. 30, 2019	289,529		$ 1	654,857	501	(365,830)
Ending balance, Shares at Jun. 30, 2019			132,776,000
Beginning Balance at Dec. 31, 2019	301,984		$ 1	705,143	(444)	(402,716)
Beginning balance, Shares at Dec. 31, 2019			136,054,000
Common stock issued upon vesting of restricted stock units, net	0
Common stock issued upon vesting of restricted stock units, net, Shares			1,996,000
Common stock issued upon stock option exercise	$ 25,629			25,629
Common stock issued upon stock option exercise, Shares	1,920,482		1,920,000
Common stock issued under employee stock purchase plan	$ 3,082			3,082
Common stock issued under employee stock purchase plan, shares			268,000
Stock-based compensation expense	38,459			38,459
Comprehensive Income (loss)	(889)	[1]			(889)
Net loss	(47,174)					(47,174)
Ending balance at Jun. 30, 2020	321,091		$ 1	772,313	(1,333)	(449,890)
Ending balance, Shares at Jun. 30, 2020			140,238,000
Beginning Balance at Mar. 31, 2020	307,391		$ 1	737,236	(2,880)	(426,966)
Beginning balance, Shares at Mar. 31, 2020			138,070,000
Common stock issued upon vesting of restricted stock units, net	0
Common stock issued upon vesting of restricted stock units, net, Shares			1,051,000
Common stock issued upon stock option exercise	11,814			11,814
Common stock issued upon stock option exercise, Shares			849,000
Common stock issued under employee stock purchase plan	3,082			3,082
Common stock issued under employee stock purchase plan, shares			268,000
Stock-based compensation expense	20,181			20,181
Comprehensive Income (loss)	1,547	[1]			1,547
Net loss	(22,924)					(22,924)
Ending balance at Jun. 30, 2020	$ 321,091		$ 1	$ 772,313	$ (1,333)	$ (449,890)
Ending balance, Shares at Jun. 30, 2020			140,238,000

[1] Net of tax effect which was not material.