Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net (loss) income	$ (2,317)	$ 1,701
Adjustment to reconcile net (loss) income to net cash provided by (used in) operating activities:
Depreciation and amortization	1,623	1,122
Amortization of software licenses	714	455
Stock-based compensation expense	8,544	3,191
Provision for doubtful accounts	31
(Benefit from) provision for deferred income taxes	(2,234)	1,357
Tax windfall benefits from stock option exercises	(8,446)
Non-cash interest expense on convertible senior notes	1,339	1,242
Other		(30)
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	6,824	6,404
Other current and long-term assets	3,451	(8,081)
Accounts payable, accrued expenses and other long-term liabilities	(3,061)	(5,311)
Current and long-term deferred revenue	(1,569)	(5,504)
Net cash provided by (used in) operating activities	4,899	(3,454)
Cash flows from investing activities:
Purchases of property and equipment	(1,111)	(978)
Purchases of marketable securities	(41,620)	(36,656)
Proceeds from maturities of marketable securities	32,469	36,334
Net cash used in investing activities	(10,262)	(1,300)
Cash flows from financing activities:
Proceeds from the exercise of stock options	168	948
Taxes paid on vesting of RSUs	(1,106)	(1,129)
Tax windfall benefits from stock option exercises	8,446
Notes payable and bank loans - payments		(376)
Net cash provided by (used in) financing activities	7,508	(557)
Effect of exchange rate changes on cash and cash equivalents	(203)	94
Net increase (decrease) in cash and cash equivalents	1,942	(5,217)
Cash and cash equivalents, beginning of period	90,545	94,072
Cash and cash equivalents, end of period	$ 92,487	$ 88,855