Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 10,789	$ 21,418
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	6,954	6,510
Amortization of intangible assets	1,670	1,779
Net (gains) losses from investments	84	(898)
Deferred income taxes	(6,461)	(9,851)
Stock-based compensation	4,588	3,921
Amortization of premium on investments	1,809	2,144
Foreign currency losses	248	382
Changes in assets and liabilities, net of acquisitions
Accounts receivable	37,570	37,196
Deferred commissions	1,002	4,127
Prepaid expenses and other current assets	3,683	3,991
Accounts payable	116	(318)
Accrued expenses and other liabilities	(4,698)	(4,327)
Deferred revenue	(25,002)	(23,308)
Net cash provided by operating activities	32,352	42,766
Cash flows from investing activities:
Purchases of property and equipment	(2,049)	(4,388)
Purchases of marketable investments	(39,636)	(85,211)
Proceeds from sales and maturities of marketable investments	85,398	73,055
Change in restricted cash		946
Other investing activity	134	66
Net cash provided by (used in) investing activities	43,847	(15,532)
Cash flows from financing activities:
Dividends paid on common stock	(9,425)	(9,481)
Repurchases of common stock	(109,193)	(26,187)
Proceeds from issuance of common stock under employee equity incentive plans	14,506	8,538
Excess tax benefits from stock-based compensation	687	401
Payment of deferred acquisition consideration	(900)	(864)
Net cash used in financing activities	(104,325)	(27,593)
Effect of exchange rate changes on cash and cash equivalents	16	212
Net decrease in cash and cash equivalents	(28,110)	(147)
Cash and cash equivalents, beginning of period	98,810	81,047
Cash and cash equivalents, end of period	$ 70,700	$ 80,900