Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (8,759)	$ (7,972)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	1,298	1,079
Bad debt expense	269	53
Stock-based compensation	5,667	3,986
Deferred rent expense	(26)	(29)
Other non-cash reconciling items	135	145
Changes in operating assets and liabilities:
Accounts receivable	5,405	1,160
Prepaid expenses and other current assets	(5,847)	(965)
Other long term assets	(3,351)	(8)
Accounts payable	(450)	(140)
Accrued expenses	(1,518)	(41)
Deferred revenue	952	4,844
Net cash (used in) provided by operating activities	(6,225)	2,112
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(6,369)	(1,620)
Purchase of marketable securities	(36,903)	(17,533)
Acquisition, net of cash acquired	(12,136)
Sale and maturity of marketable securities	17,225	14,825
Change in restricted cash and other assets	(16)	(185)
Net cash used in investing activities	(38,199)	(4,513)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	3,348	314
Proceeds from issuance of notes payable		574
Payments of equipment notes	(610)	(682)
Payments of software financing agreement	(766)	(232)
Net cash provided by (used in) financing activities	1,972	(26)
EFFECT OF EXCHANGE RATES ON CASH AND CASH EQUIVALENTS	7	(101)
DECREASE IN CASH AND CASH EQUIVALENTS	(42,445)	(2,528)
CASH AND CASH EQUIVALENTS-Beginning of period	242,425	58,877
CASH AND CASH EQUIVALENTS-End of period	199,980	56,349
SUPPLEMENTARY INFORMATION:
Interest paid	56	76
Income taxes paid	398	138
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchase of property and equipment included in accounts payable and accrued expenses	$ 675	$ 76