Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 40,745	$ 25,049
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	4,180	3,904
Bad debt provisions	564
Realized gains on sales of short term investments	(603)	(589)
Deferred income taxes	(715)	(1,754)
Compensation expense related to restricted stock	856	652
Adjustment related to the uncertain tax positions and other tax credits		10
Changes in assets and liabilities:
Accounts receivable and revenue earned in excess of billings	(9,737)	(4,107)
Other assets	(13,084)	(2,752)
Accrued payroll and other liabilities	(4,713)	(4,597)
Deferred revenue	(3,976)	(3,769)
Net cash provided by operating activities	13,517	12,047
CASH FLOWS FROM INVESTING ACTIVITIES:
Property and equipment expenditures	(4,489)	(20,930)
Purchase of mutual funds	(57,675)	(39,501)
Purchase of term deposits with banks	(76,414)	(50,252)
Proceeds from sales of mutual funds	58,067	52,789
Maturities of term deposits with banks	50,433	37,934
Net cash used in by investing activities	(30,078)	(19,960)
CASH FLOWS FROM FINANCING ACTIVITIES:
Dividends paid	(2,494)	(2,493)
Net cash used in financing activities	(2,494)	(2,493)
Effect of foreign currency exchange rate changes on cash	(1,724)	1,425
Change in cash and cash equivalents	(20,779)	(8,981)
Cash and cash equivalents, beginning of period	104,628	78,505
Cash and cash equivalents, end of period	83,849	69,524
Non cash investing and financing activities:
Cash dividends declared but unpaid	2,494	2,754
Cash paid for income taxes	$ 7,977	$ 858