CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
OPERATING ACTIVITIES:
Net loss	$ (18,627)	$ (23,987)	$ (55,628)	$ (42,877)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Stock-based compensation expense	15,900	9,300	30,642	16,471
Depreciation and amortization			11,274	7,643
Amortization of tenant allowance			(258)	(258)
Amortization of purchased intangibles			1,378	1,469
Amortization of debt issuance costs			600	376
Accretion of debt discount on convertible senior notes			4,777	2,990
Changes in fair value of contingent consideration			(263)	0
Provision for doubtful accounts			1,953	938
Deferred income taxes			54	114
Changes in operating assets and liabilities:
Accounts receivable			10,051	(6,383)
Prepaid expenses and other current assets			(5,377)	(6,069)
Contract acquisition costs noncurrent			(4,348)	(6,635)
Other assets			(28)	(169)
Accounts payable			(3,026)	(418)
Accrued expenses and other current liabilities			14,235	(11,114)
Deferred revenue			5,979	14,832
Operating lease liabilities			270	0
Other liabilities			21	178
Net cash provided by (used in) operating activities			12,306	(28,912)
INVESTING ACTIVITIES:
Purchases of property and equipment, including capitalized software			(23,611)	(21,382)
Payments for intangible assets			(648)	(293)
Net cash used in investing activities			(24,259)	(21,675)
FINANCING ACTIVITIES:
Repurchase of common stock			0	(709)
Proceeds from issuance of common stock in connection with the exercise of options and ESPP			9,123	10,953
Proceeds from issuance of convertible senior notes			0	230,000
Payment of issuance costs in connection with convertible senior notes			0	(7,587)
Payments related to contingent consideration			0	(487)
Purchase of capped call option			0	(23,184)
Net cash provided by financing activities			9,123	208,986
EFFECT OF FOREIGN EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS			(516)	(121)
CHANGE IN CASH AND CASH EQUIVALENTS			(3,346)	158,278
CASH AND CASH EQUIVALENTS - Beginning of the period			176,523	66,449	$ 66,449
CASH AND CASH EQUIVALENTS - End of the period	$ 173,177	$ 224,727	173,177	224,727	$ 176,523
SUPPLEMENTAL DISCLOSURE OF OTHER CASH FLOW INFORMATION:
Cash paid for income taxes			3,124	1,606
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchase of property and equipment recorded in accounts payable			1,198	861
Issuance of 11,508 shares of common stock as earnout payment in connection with AdvantageTec Inc.			$ 294	0
Issuance of 11,508 shares of common stock as earnout payment in connection with AdvantageTec Inc. (shares)			11,508
Issuance of 991,905 shares of common stock to settle cash awards			$ 24,656	0
Issuance of 991,905 shares of common stock to settle cash awards (shares)			991,905
Operating lease right of use asset			$ (1,050)	12,807
Operating lease liabilities- short-term and long term			(2,561)	(16,782)
Debt offering costs, accrued but not paid			$ 0	$ 1,048