Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net income	$ 100,627	$ 88,427
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	12,427	11,059
Amortization of operating lease right-of-use assets	2,835
Stock-based compensation expense	11,125	7,601
Deferred taxes	1,631	1,448
Other	(296)	1,014
Changes in operating assets and liabilities:
(Increase) in accounts receivable	(8,883)	(9,350)
(Increase) in prepaid expenses and other assets	(131)	(2,330)
Decrease (increase) in trading investments	8,854	(3,288)
(Decrease) in accrued employee compensation	(12,384)	(12,890)
(Decrease) in income and other tax liabilities	(3,661)	(1,164)
Increase in deferred revenue	1,000	935
(Decrease) increase in accounts payable, accrued expenses and other liabilities	(877)	5,559
(Decrease) in operating lease liabilities	(1,422)
Net cash provided by operating activities	109,102	85,818
Cash flows from investing activities
Proceeds from maturities and sales, available-for-sale investments	130,875	152,335
Purchases, available-for-sale investments	(128,189)	(159,192)
Purchases of furniture, equipment and leasehold improvements	(6,114)	(16,035)
Capitalization of software development costs	(7,310)	(6,536)
Other	2	16
Net cash (used in) investing activities	(10,736)	(29,412)
Cash flows from financing activities
Cash dividend on common stock	(38,323)	(31,350)
Exercise of stock options	522	371
Withholding tax payments on restricted stock vesting and stock option exercises	(12,061)	(7,997)
Repurchases of common stock	(8,670)	(12,904)
Net cash (used in) financing activities	(58,532)	(51,880)
Effect of exchange rate changes on cash and cash equivalents	21	(854)
Cash and cash equivalents including restricted cash
Net increase for the period	39,855	3,672
Beginning of period	247,458	167,014
End of period	287,313	170,686
Mutual Funds Held In Rabbi Trust [Member]
Changes in operating assets and liabilities:
Decrease (increase) in trading investments	$ (1,743)	$ (1,203)

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