CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 111,848	$ 100,600
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	7,362	7,749
Provision (benefit) for doubtful accounts / advances	38	(68)
Realized gains on sales of short term investments	(2,477)	(6,226)
Deferred income taxes	(2,517)	(805)
Compensation expense related to restricted stock	3,682	3,414
Unrealized foreign exchange loss	406	916
Changes in assets and liabilities:
Accounts receivable and revenue earned in excess of billings	1,259	(15,117)
Other current assets	(5,261)	(20,664)
Accounts payable, accrued payroll and other liabilities	(1,004)	4,012
Deferred revenue	(3,686)	(336)
Net cash provided by operating activities	109,650	73,475
CASH FLOWS FROM INVESTING ACTIVITIES:
Property and equipment expenditures	(9,133)	(10,131)
Proceeds from sale of property and equipment	157	83
Purchase of mutual funds	(92,702)	(53,272)
Purchase of term deposits with banks	(219,235)	(134,809)
Proceeds from sales of mutual funds	135,179	118,265
Maturities of term deposits with banks	314,845	303,923
Net cash provided by investing activities	129,111	224,059
CASH FLOWS FROM FINANCING ACTIVITIES:
Excess tax benefits on stock-based compensation plans	23	295
Proceeds from loans and borrowings	60,250
Repayment of loans and borrowings	(93,125)	(4,125)
Net cash used in financing activities	(32,852)	(3,830)
Effect of foreign currency exchange rate changes on cash	(3,962)	(1,529)
Change in cash and cash equivalents	201,947	292,175
Cash and cash equivalents, beginning of period	500,499	197,708
Cash and cash equivalents, end of period	702,446	489,883
Supplemental disclosures of cash flow information:
Cash paid for income taxes	37,540	26,641
Cash paid for interest	$ 1,152	$ 1,112