Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities
Net (loss) income	$ 2,334	$ (7,167)
Adjustments to reconcile net (loss) income to net cash provided by operating activities
Depreciation and amortization	5,499	3,596
Amortization of premium on investments	122	77
Provision for bad debts	32	41
Provision for deferred income taxes	268	198
Stock-based compensation	12,151	10,282
Gain on disposal of equipment	(1)	(1)
Changes in assets and liabilities:
Accounts receivable	2,575	3,601
Prepaid expenses and other current assets	(1,009)	(3,388)
Other assets	210	(1,794)
Accounts payable	433	(2,409)
Accrued liabilities	(1,327)	1,997
Deferred revenue	23,394	8,052
Other long-term liabilities	721	(174)
Net cash provided by operating activities	45,402	12,911
Cash flows from investing activities
Purchases of marketable securities	(19,984)	(60,381)
Proceeds from sale or disposal of marketable securities	20,000	60,000
Purchases of property and equipment	(4,348)	(6,456)
Intangible asset additions	(1,322)	(915)
Cash paid for acquisition, net of cash acquired	(7,434)
Decrease (increase) in restricted cash and deposits	(200)	125
Net cash used in investing activities	(13,288)	(7,627)
Cash flows from financing activities
Proceeds from issuance of common stock upon option exercises	10,306	267
Income tax benefit from the exercise of stock options		2
Common stock withheld to satisfy income tax withholdings for restricted stock unit vesting	(3,557)	(917)
Purchase of treasury stock	(6,949)	(14,607)
Net cash used in financing activities	(200)	(15,255)
Effect of exchange rate changes on cash and cash equivalents and restricted cash	(343)	(883)
Net (decrease) increase in cash and cash equivalents	31,571	(10,854)
Cash and cash equivalents, beginning of period	89,257	111,932
Cash and cash equivalents, end of period	120,828	101,078
Supplemental disclosure of cash flow information
Cash paid for interest	2
Cash paid for income taxes	568	6,287
Noncash investing and financing activities
Purchases of property and equipment included in accounts payable and accrued liabilities	687	1,515
Fair value of contingent consideration in connection with acquisition included in accrued liabilities and other long term liabilities		$ 176