Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net income	$ 185,543	$ 122,856	$ 113,593
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,445	16,880	14,413
Provision for doubtful debts / advances	1,101	97	65
Realized gains on sales of short-term investments	(3,012)	(2,539)	(1,349)
Deferred income taxes	(1,343)	(4,613)	(8,287)
Compensation expense related to restricted stock	3,725	2,684	1,938
Uncertain tax positions and other tax credits	0	(3,948)	(1,284)
Gain on sale of property and equipment	(977)	0	0
Changes in assets and liabilities:
Accounts receivable and revenue earned in excess of billings	(10,065)	(40,907)	(20,286)
Other current assets	(15,751)	(9,183)	(11,844)
Accrued payroll and other liabilities	19,742	27,399	23,224
Deferred revenues	(4,720)	326	3,829
Net cash provided by operating activities	188,688	109,052	114,012
Cash flows from investing activities:
Property and equipment expenditures	(32,255)	(38,232)	(22,546)
Proceeds from sale of property and equipment	1,445	0	0
Purchases of mutual funds	(270,685)	(213,829)	(292,745)
Purchases of term deposits with banks	(277,116)	(206,201)	(248,454)
Proceeds from sales of mutual funds	238,604	219,032	289,247
Maturities of term deposits with banks	194,873	159,566	181,007
Net cash used in investing activities	(145,134)	(79,664)	(93,491)
Cash flows from financing activities:
Net proceeds from issuance of common stock	0	2	947
Excess tax benefits on stock-based compensation plans	645	0	152
Proceeds from loans and borrowings	50,000	0	0
Interest on loans and borrowings	29	0	0
Dividends paid	(106,231)	(9,992)	(30,697)
Net cash used in financing activities	(55,557)	(9,990)	(29,598)
Effect of foreign currency exchange rate changes on cash	1,997	6,725	(241)
Change in cash and cash equivalents	(10,006)	26,123	(9,317)
Cash and cash equivalents, beginning of year	104,628	78,505	87,822
Cash and cash equivalents, end of year	94,622	104,628	78,505
Non cash investing and financing activities
Cash dividends declared but unpaid		2,494	2,490
Cash paid for income taxes	$ 48,596	$ 28,610	$ 19,403