Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities
Net income	$ 62,089	$ 48,831
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	9,221	9,215
Stock-based compensation expense	6,937	6,025
Deferred taxes	307	858
Other	646	1,201
Changes in operating assets and liabilities:
(Increase) in accounts receivable	(22,677)	(13,197)
(Increase) in prepaid expenses and other assets	(3,574)	(5,907)
(Decrease) in accrued employee compensation	(9,084)	(9,201)
(Decrease) increase in income and other tax liabilities	(1,856)	1,336
Increase in deferred revenue	294	185
Increase in accounts payable, accrued expenses and other liabilities	2,708	1,249
Net cash (used in) provided by operating activities	(28,669)	40,595
Available-for-sale investments:
Proceeds from maturities	20,000	15,328
Purchases	(8,065)	(19,098)
Purchases of furniture, equipment and leasehold improvements	(3,904)	(2,345)
Capitalization of software development costs	(6,142)	(4,816)
Other	99	(4)
Net cash provided by (used in) investing activities	1,988	(10,935)
Cash flows from financing activities
Cash dividend on common stock	(19,313)	(14,862)
Exercise of stock options	2,138	990
Withholding tax payments on restricted stock vesting and stock option exercises	(5,585)	(4,243)
Excess tax benefits from stock-based compensation	8,573	3,755
Repurchases of common stock	(5,400)	(14,464)
Net cash (used in) financing activities	(19,587)	(28,824)
Effect of exchange rate changes on cash and cash equivalents	(185)	(497)
Cash and cash equivalents
Net (decrease) increase for the period	(46,453)	339
Beginning of period	199,728	168,924
End of period	153,275	$ 169,263
Corporate Debt [Member]
Changes in operating assets and liabilities:
(Increase) in trading securities	(72,396)
Mutual Funds Held In Rabbi Trust [Member]
Changes in operating assets and liabilities:
(Increase) in trading securities	$ (1,284)