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		$ 0	0	0	2,693
Common stock issued upon vesting of restricted stock units	0		$ 0	0	0	0
Common stock issued upon vesting of restricted stock units, Shares			2,860,000
Common stock issued upon stock option exercise	41,986		$ 0	41,986	0	0
Common stock issued upon stock option exercise, Shares			3,319,000
Common stock issued in connection with acquisitions	36,204		$ 0	36,204	0	0
Common stock issued in connection with acquisitions, shares			2,320,000
Common stock issued under employee stock purchase plan	2,662		$ 0	2,662	0	0
Common stock issued under employee stock purchase plan, shares			261,000
Stock-based compensation expense	47,936		$ 0	47,936	0	0
Comprehensive income (loss)	(2,162)	[1]	0	0	(2,162)	0
Other	232		$ 0	232	0	0
Other, Shares			16,000
Net loss	(52,565)		$ 0	0	0	(52,565)
Ending balance at Sep. 30, 2019	296,369		$ 1	680,957	(2,449)	(382,140)
Ending balance, Shares at Sep. 30, 2019			134,594,000
Beginning Balance at Jun. 30, 2019	289,529		$ 1	654,857	501	(365,830)
Beginning balance, Shares at Jun. 30, 2019			132,776,000
Common stock issued upon vesting of restricted stock units	0		$ 0	0	0	0
Common stock issued upon vesting of restricted stock units, Shares			1,080,000
Common stock issued upon stock option exercise	4,348		$ 0	4,348	0	0
Common stock issued upon stock option exercise, Shares			362,000
Common stock issued in connection with acquisitions	6,112		$ 0	6,112	0	0
Common stock issued in connection with acquisitions, shares			376,000
Stock-based compensation expense	15,640		$ 0	15,640	0	0
Comprehensive income (loss)	(2,950)	[1]	0	0	(2,950)	0
Net loss	(16,310)		0	0	0	(16,310)
Ending balance at Sep. 30, 2019	296,369		$ 1	680,957	(2,449)	(382,140)
Ending balance, Shares at Sep. 30, 2019			134,594,000
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	0		$ 0	0	0	0
Common stock issued upon vesting of restricted stock units, Shares			3,134,000
Common stock issued upon stock option exercise	$ 37,506		$ 0	37,506	0	0
Common stock issued upon stock option exercise, Shares	2,743,310		2,743,000
Common stock issued under employee stock purchase plan	$ 3,082		$ 0	3,082	0	0
Common stock issued under employee stock purchase plan, shares			268,000
Stock-based compensation expense	60,271		$ 0	60,271	0	0
Comprehensive income (loss)	2,251	[1]	0	0	2,251	0
Net loss	(73,293)		0	0	0	(73,293)
Ending balance at Sep. 30, 2020	331,801		$ 1	806,002	1,807	(476,009)
Ending balance, Shares at Sep. 30, 2020			142,199,000
Beginning Balance at Jun. 30, 2020	321,091		$ 1	772,313	(1,333)	(449,890)
Beginning balance, Shares at Jun. 30, 2020			140,238,000
Common stock issued upon vesting of restricted stock units	0		$ 0	0	0	0
Common stock issued upon vesting of restricted stock units, Shares			1,138,000
Common stock issued upon stock option exercise	11,877		$ 0	11,877	0	0
Common stock issued upon stock option exercise, Shares			823,000
Stock-based compensation expense	21,812		$ 0	21,812	0	0
Comprehensive income (loss)	3,140	[1]	0	0	3,140	0
Net loss	(26,119)		0	0	0	(26,119)
Ending balance at Sep. 30, 2020	$ 331,801		$ 1	$ 806,002	$ 1,807	$ (476,009)
Ending balance, Shares at Sep. 30, 2020			142,199,000

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