Condensed Consolidated Statements of Cash Flows (USD $)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities
Net income (loss)	$ (7,166,596)	$ 651,917
Adjustments to reconcile net income (loss) to net cash provided by operating activities
Depreciation and amortization	3,596,005	2,848,825
Amortization of premium on investments	76,689	22,370
Provision for bad debts	40,929	55,000
Provision for deferred income taxes	198,398	173
Stock-based compensation	10,281,755	6,073,007
Gain on disposal of equipment	(700)	(661)
Changes in assets and liabilities:
Accounts receivable	3,601,368	441,348
Prepaid expenses and other current assets	(3,388,388)	(513,585)
Other assets	(1,794,613)	11,355
Accounts payable	(2,408,753)	(871,267)
Accrued liabilities	1,997,040	2,235,628
Deferred revenue	8,051,992	4,138,268
Other long-term liabilities	(173,879)	1,053,721
Net cash provided by operating activities	12,911,247	16,146,099
Cash flows from investing activities
Purchases of marketable securities	(60,381,150)	(74,987,000)
Proceeds from sale or disposal of marketable securities	60,000,000	70,000,000
Purchases of property and equipment	(6,456,043)	(2,284,816)
Intangible asset additions	(914,633)	(566,442)
Cash paid for acquisition, net of cash acquired		(14,831,525)
(Increase) decrease in restricted cash and deposits	125,000	(3,557,760)
Net cash used in investing activities	(7,626,826)	(26,227,543)
Cash flows from financing activities
Proceeds from issuance of common stock upon option exercises	266,976	2,012,777
Income tax benefit from the exercise of stock options	2,000	2,552,000
Common stock withheld to satisfy income tax withholdings for restricted stock unit vesting	(917,488)
Purchase of treasury stock	(14,606,982)
Net cash provided by (used in) financing activities	(15,255,494)	4,564,777
Effect of exchange rate changes on cash and cash equivalents and restricted cash	(882,919)	356,524
Net decrease in cash and cash equivalents	(10,853,992)	(5,160,143)
Cash and cash equivalents, beginning of period	111,931,599	103,603,684
Cash and cash equivalents, end of period	101,077,607	98,443,541
Supplemental disclosure of cash flow information
Cash paid for interest	73	215
Cash paid for income taxes	6,286,667	380,787
Noncash investing and financing activities
Purchases of property and equipment included in accounts payable and accrued liabilities	1,514,742	871,749
Fair value of contingent consideration in connection with acquisition included in accrued liabilities and other long term liabilities	$ 176,454	$ 234,568