Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net income	$ 52,522	$ 47,940
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,082	5,269
Amortization of operating lease right-of-use assets	1,291
Stock-based compensation expense	5,196	3,951
Deferred taxes	2,022	2,061
Other	(587)	(186)
Changes in operating assets and liabilities:
(Increase) in accounts receivable	(13,453)	(14,955)
Decrease in prepaid expenses and other assets	5,264	852
Decrease (Increase) in trading securities	6,015	3,054
(Decrease) in accrued employee compensation	(22,354)	(20,891)
Increase in income and other tax liabilities	2,267	4,304
Increase in deferred revenue	735	894
(Decrease) increase in accounts payable, accrued expenses and other liabilities	(3,764)	307
(Decrease) in operating lease liabilities	(321)
Net cash provided by operating activities	39,369	31,439
Cash flows from investing activities
Proceeds from maturities and sales, available-for-sale investments	67,603	51,002
Purchases, available-for-sale investments	(53,193)	(57,839)
Purchases of furniture, equipment and leasehold improvements	(649)	(2,278)
Capitalization of software development costs	(3,184)	(3,590)
Other	(15)	(24)
Net cash provided by (used in) investing activities	10,562	(12,729)
Cash flows from financing activities
Cash dividend on common stock	(19,412)	(15,814)
Exercise of stock options	172	258
Withholding tax payments on restricted stock vesting and stock option exercises	(11,803)	(7,621)
Repurchases of common stock	(5,184)	(6,268)
Net cash (used in) financing activities	(36,227)	(29,445)
Effect of exchange rate changes on cash and cash equivalents	943	(110)
Cash and cash equivalents including restricted cash
Net increase (decrease) for the period	14,647	(10,845)
Beginning of period	247,458	168,150
End of period	262,105	157,305
Mutual Funds Held In Rabbi Trust [Member]
Changes in operating assets and liabilities:
Decrease (Increase) in trading securities	$ (1,546)	$ (1,161)

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