Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
OPERATING ACTIVITIES:
Net loss	$ (25,032)	$ (18,191)	$ (25,873)
Adjustments to reconcile net loss to net cash provided by operating activities:
Stock-based compensation expense	14,841	8,944	9,736
Depreciation	14,188	12,358	12,011
Impairment on investments	0	0	2,600
Amortization of tenant allowance	(326)	(166)	(180)
Amortization of purchased intangibles	2,813	4,682	6,673
Provision for doubtful accounts, net	1,788	1,895	1,831
Deferred income taxes	(309)	(2,397)	1,852
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(9,662)	(7,998)	(3,265)
Prepaid expenses and other current assets	(14,628)	(1,867)	3,845
Other assets	(107)	(38)	196
Accounts payable	2,199	(2,743)	185
Accrued expenses and other current liabilities	(205)	7,838	2,982
Deferred revenue	19,005	8,418	13,283
Other liabilities	214	(445)	(1,316)
Net cash provided by operating activities	4,779	10,290	24,560
INVESTING ACTIVITIES:
Purchases of property and equipment, including capitalized software	(21,938)	(17,390)	(12,344)
Payments for acquisitions and intangible assets, net of cash acquired	(7,286)	(441)	(555)
Cash held as collateral	1,451	2,511	1,447
Net cash used in investing activities	(27,773)	(15,320)	(11,452)
FINANCING ACTIVITIES:
Repurchase of common stock	(1,345)	(1,742)	(9,967)
Proceeds from issuance of common stock in connection with the exercise of options	35,271	8,951	2,899
Net cash provided by (used in) financing activities	33,926	7,209	(7,068)
EFFECT OF FOREIGN EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	(598)	3,047	(3,954)
CHANGE IN CASH AND CASH EQUIVALENTS	10,334	5,226	2,086
CASH AND CASH EQUIVALENTS - Beginning of the year	56,115	50,889	48,803
CASH AND CASH EQUIVALENTS - End of the year	66,449	56,115	50,889
SUPPLEMENTAL DISCLOSURE OF OTHER CASH FLOW INFORMATION:
Cash paid for income taxes	5,144	1,551	424
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchase of property and equipment recorded in accounts payable	190	936	2,497
Leasehold improvements funded by landlord	1,551	0	1,440
BotCentral
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)	85,861,000
Conversable
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Issuance of shares of common stock in connection with acquisition	$ 2,850	0	0
Issuance of shares of common stock in connection with acquisition (in shares)	115,385,000
Fair value of contingent earn-out in connection with the acquisition recorded in accrued expenses	$ 1,496	0	0
AdvantageTec
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Issuance of shares of common stock in connection with acquisition	$ 4,300	0	0
Issuance of shares of common stock in connection with acquisition (in shares)	117,082,000
Fair value of contingent earn-out in connection with the acquisition recorded in accrued expenses	$ 876	$ 0	$ 0