CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
OPERATING ACTIVITIES:
Net loss	$ (11,524)	$ (13,209)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Stock-based compensation expense	6,264	4,260
Depreciation	6,786	5,838
Amortization of purchased intangibles	1,422	2,860
Amortization of tenant allowance	(83)	(83)
Deferred income taxes	41	(13)
Provision for doubtful accounts, net	862	958
Changes in operating assets and liabilities:
Accounts receivable	(1,045)	6,011
Prepaid expenses and other current assets	(9,531)	(3,864)
Other assets	(187)	(31)
Accounts payable	34	(3,881)
Accrued expenses and other current liabilities	(8,771)	(3,204)
Deferred revenue	13,943	9,477
Other liabilities	(218)	245
Net cash (used in) provided by operating activities	(2,007)	5,364
INVESTING ACTIVITIES:
Purchases of property and equipment, including capitalized software	(9,664)	(7,011)
Cash held as collateral for foreign exchange forward contracts	1,235	205
Payments for acquisitions and intangible assets, net of cash acquired	(392)	(239)
Net cash used in investing activities	(8,821)	(7,045)
FINANCING ACTIVITIES:
Proceeds from issuance of common stock in connection with the exercise of options	25,667	2,588
Repurchase of common stock	(1,345)	(1,781)
Net cash provided by financing activities	24,322	807
EFFECT OF FOREIGN EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	138	4,350
CHANGE IN CASH AND CASH EQUIVALENTS	13,632	3,476
CASH AND CASH EQUIVALENTS - Beginning of the period	56,115	50,889
CASH AND CASH EQUIVALENTS - End of the period	69,747	54,365
SUPPLEMENTAL DISCLOSURE OF OTHER CASH FLOW INFORMATION:
Cash paid for income taxes	5,553	659
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchase of property and equipment recorded in accounts payable	774	41
Noncash or Part Noncash Acquisition, Costs	$ 1,000	$ 0