Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating activities:
Net income (loss)	$ 10,108	$ (5,891)	$ 32,212
Adjustment to reconcile net income (loss) to cash provided by operating activities:
Excess tax benefits from exercise or vesting of equity awards	(6,658)	(3,719)	(15,411)
Deferred income taxes	(15,269)	(1,574)	1,413
Depreciation and amortization	17,073	10,838	2,801
Amortization of investments	849	994	3,910
Stock-based compensation expense	9,028	6,745	4,673
Foreign currency transaction loss	977	4,753
Other	58	(95)	113
Change in operating assets and liabilities:
Trade accounts receivable	(18,504)	(23,365)	8,458
Income taxes receivable	1,721	(4,220)	(5,046)
Other current assets	8,798	3,003	502
Accounts payable and accrued expenses	9,041	4,515	16,311
Deferred revenue	14,595	23,927	639
Other long-term assets and liabilities	7,998	2,503	(994)
Cash provided by operating activities	39,815	18,414	49,581
Investing activities:
Purchases of marketable securities	(57,249)	(73,619)	(79,447)
Proceeds from maturities and called marketable securities	20,648	34,426	67,327
Sale of marketable securities	1,048	161,260
Payments for 2010 acquisition, net of cash acquired		(109,228)
Contingent consideration paid for a 2008 acquisition		(250)
Investment in property and equipment	(9,835)	(5,748)	(6,043)
Cash provided by (used in) investing activities	(45,388)	6,841	(18,163)
Financing activities:
Issuance of common stock for share-based compensation plans	2,622	2,863	4,808
Excess tax benefits from exercise or vesting of equity awards	6,658	3,719	15,411
Dividend payments to shareholders	(4,495)	(4,441)	(4,346)
Common stock repurchases for tax withholdings for net settlement of equity awards	(6,262)	(6,984)	(8,596)
Common stock repurchases under share repurchase programs	(4,835)	(8,408)	(12,326)
Cash used in financing activities	(6,312)	(13,251)	(5,049)
Effect of exchange rate on cash and cash equivalents	1,111	(4,734)	1,401
Net (decrease) increase in cash and cash equivalents	(10,774)	7,270	27,770
Cash and cash equivalents, beginning of year	71,127	63,857	36,087
Cash and cash equivalents, end of year	60,353	71,127	63,857
Supplemental disclosures:
Income taxes paid	2,566	1,582	7,024
Non-cash investing and financing activity:
Dividends payable	$ 1,132	$ 1,118	$ 1,105