CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 47,550	$ 27,348
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	19,985	17,308
Share-based compensation expense	17,302	14,416
Operating lease right-of-use assets expense	1,457	1,165
Deferred income tax benefit	(2,668)	(4,785)
Changes in operating assets and liabilities, exclusive of effects of    acquired companies:
Accounts receivable	56,982	9,622
Income tax receivable	(10,175)	12,425
Prepaid expenses and other current assets	(11,186)	(3,862)
Accounts payable	(2,020)	(1,501)
Operating lease liabilities	(1,743)	(1,272)
Accrued liabilities	(12,210)	(3,760)
Deferred revenue	(46,568)	(43,147)
Net cash provided by operating activities	56,706	23,957
Cash flows from investing activities:
Additions to property and equipment	(9,349)	(12,320)
Purchase of marketable security investments	(27,271)	(3,590)
Proceeds from marketable security investments	18,237	20,276
Purchase of investment in common shares	(10,000)	0
Proceeds from the sale of investment in preferred shares	15,000	0
Investment in software	(1,315)	(690)
Cost of acquisitions, net of cash acquired	(261)	(199,130)
(Increase) decrease in other	(48)	564
Net cash used by investing activities	(15,007)	(194,890)
Cash flows from financing activities:
Increase in net borrowings on revolving line of credit	0	85,000
Purchase of treasury shares	(15,482)	(17,786)
Payment of contingent consideration	(5,619)	0
Proceeds from exercise of stock options	46,236	6,528
Contributions from employee stock purchase plan	2,469	2,349
Net cash provided by financing activities	27,604	76,091
Net increase (decrease) in cash and cash equivalents	69,303	(94,842)
Cash and cash equivalents at beginning of period	232,682	134,279
Cash and cash equivalents at end of period	$ 301,985	$ 39,437