Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (11,840)	$ (5,280)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	3,687	2,738
Consulting expense settled with equity awards		286
Bad debt expense	667	397
Stock-based compensation	10,353	7,056
Deferred income taxes	35	(5,807)
Amortization of premium on marketable securities	92	101
Other non-cash reconciling items	3	95
Changes in operating assets and liabilities:
Accounts receivable	10,348	11,662
Prepaid expenses and other current assets	(2,215)	(1,736)
Accounts payable	40	(693)
Accrued expenses	(9,897)	(7,691)
Deferred revenue	2,173	831
Other assets and liabilities	11	(13)
Net cash provided by operating activities	3,457	1,946
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(6,469)	(6,809)
Purchase of marketable securities	(20,237)	(24,569)
Sale and maturity of marketable securities	24,298	33,192
Acquisition, net of cash acquired		(54,733)
Net cash used in investing activities	(2,408)	(52,919)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	1,457	2,177
Net cash provided by financing activities	1,457	2,177
EFFECT OF EXCHANGE RATES ON CASH AND CASH EQUIVALENTS	346	(731)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	2,852	(49,527)
CASH AND CASH EQUIVALENTS—Beginning of period	114,989	158,827
CASH AND CASH EQUIVALENTS—End of period	117,841	109,300
SUPPLEMENTARY INFORMATION:
Income taxes paid	398	100
NONCASH INVESTING AND FINANCING ACTIVITIES:
Purchase of property and equipment included in accounts payable and accrued expenses	$ 1,641	$ 1,653