Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
OPERATING ACTIVITIES:
Net loss	$ (96,071)	$ (25,032)	$ (18,191)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Stock-based compensation expense	44,105	14,841	8,944
Depreciation and amortization	16,366	14,188	12,358
Amortization of tenant allowance	(516)	(326)	(166)
Amortization of purchased intangibles	2,932	2,813	4,682
Amortization of debt issuance costs	956	0	0
Accretion of debt discount on convertible senior notes	7,605	0	0
Change in fair value of contingent consideration	(328)	0	0
Provision for doubtful accounts, net	2,159	1,788	1,895
Deferred income taxes	(1,207)	(309)	(2,397)
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(43,757)	(9,662)	(7,998)
Prepaid expenses and other current assets	(4,712)	(12,993)	9,270
Contract acquisition costs noncurrent	(13,718)	(1,635)	(11,137)
Other assets	(30)	(107)	(38)
Accounts payable	3,808	2,199	(2,743)
Accrued expenses and other current liabilities	(10,882)	(205)	7,838
Deferred revenue	33,953	19,005	8,418
Increase in operating lease liability	388	0	0
Other liabilities	(209)	214	(445)
Net cash (used in) provided by operating activities	(59,158)	4,779	10,290
INVESTING ACTIVITIES:
Purchases of property and equipment, including capitalized software	(47,582)	(21,938)	(17,390)
Payments for acquisitions and intangible assets, net of cash acquired	(924)	(7,286)	(441)
Cash held as collateral	0	1,451	2,511
Net cash used in investing activities	(48,506)	(27,773)	(15,320)
FINANCING ACTIVITIES:
Repurchase of common stock	(903)	(1,345)	(1,742)
Proceeds from issuance of common stock in connection with the exercise of options and ESPP	21,060	35,271	8,951
Proceeds from issuance of convertible senior notes	230,000	0	0
Payment of issuance costs in connection with convertible senior notes	(8,635)	0	0
Payment related to contingent consideration	(487)	0	0
Purchase of capped call option	(23,184)	0	0
Net cash provided by financing activities	217,851	33,926	7,209
EFFECT OF FOREIGN EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	(113)	(598)	3,047
CHANGE IN CASH AND CASH EQUIVALENTS	110,074	10,334	5,226
CASH AND CASH EQUIVALENTS - Beginning of the year	66,449	56,115	50,889
CASH AND CASH EQUIVALENTS - End of the year	176,523	66,449	56,115
SUPPLEMENTAL DISCLOSURE OF OTHER CASH FLOW INFORMATION:
Cash paid for income taxes	3,304	5,144	1,551
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchase of property and equipment recorded in accounts payable	1,198	190	936
Leasehold improvements funded by landlord	0	1,551	0
Operating lease right of use asset (1)	21,588
Operating lease liabilities- short-term and long term	(19,467)
Conversable Dec 13 2019
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Issuance of shares of common stock in connection with acquisition	$ 1,000	0	0
Issuance of shares of common stock in connection with acquisition (in shares)	38,462
BotCentral
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Issuance of shares of common stock in connection with acquisition	$ 0	$ 1,000	0
Issuance of shares of common stock in connection with acquisition (in shares)		85,861
Conversable Sep 27 2018
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Issuance of shares of common stock in connection with acquisition	0	$ 2,850	0
Issuance of shares of common stock in connection with acquisition (in shares)		115,385
Conversable Inc
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Fair value of contingent earn-out in connection with the acquisition recorded in accrued expenses	0	$ 1,496	0
AdvantageTec
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Issuance of shares of common stock in connection with acquisition	0	$ 4,300	0
Issuance of shares of common stock in connection with acquisition (in shares)		178,082
Fair value of contingent earn-out in connection with the acquisition recorded in accrued expenses	$ 0	$ 876	$ 0