Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 161,458	$ 194,820	$ 146,527
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	135,624	81,657	76,672
Share-based compensation expense	104,726	67,365	59,967
Provision for losses and sales adjustments - accounts receivable	2,831	3,517	1,636
Operating lease right-of-use assets - non cash	10,216	5,782	5,397
Deferred income tax benefit	(13,271)	(7,936)	(6,088)
Changes in operating assets and liabilities, exclusive of effects of    acquired companies:
Accounts receivable	17,608	(10,733)	(65,738)
Income tax receivable	10,258	(15,117)	(1,925)
Prepaid expenses and other current assets	(23,863)	(8,304)	(8,976)
Accounts payable	(44,947)	(967)	7,403
Operating lease liabilities	(6,952)	(6,549)	(6,113)
Accrued liabilities	(24,822)	2,870	1,516
Deferred revenue	44,874	48,684	44,442
Increase in other long-term liabilities	(1,987)	0	0
Net cash provided by operating activities	371,753	355,089	254,720
Cash flows from investing activities:
Additions to property and equipment	(33,919)	(22,690)	(37,236)
Purchase of marketable security investments	(77,450)	(156,618)	(54,742)
Proceeds from marketable security investments	131,449	82,742	70,796
Purchase of investment in common shares	0	(10,000)	0
Proceeds from the sale of investment in preferred shares	0	15,000	0
Investment in software	(21,693)	(5,776)	(4,804)
Cost of acquisitions, net of cash acquired	(2,089,706)	(1,292)	(218,734)
Other	384	314	(295)
Net cash used by investing activities	(2,090,935)	(98,320)	(245,015)
Cash flows from financing activities:
Net borrowings on revolving credit facility	0	0	0
Payment on term loans	(145,000)	0	0
Proceeds from term loans	900,000	0	0
Proceeds from issuance of convertible senior notes	600,000	0	0
Payment of debt issuance costs	(27,165)	0	0
Purchase of treasury shares	(12,977)	(15,484)	(17,786)
Payment of contingent consideration	0	(5,619)	0
Proceeds from exercise of stock options	96,714	124,363	96,908
Contributions from employee stock purchase plan	13,158	10,912	9,576
Net cash provided by financing activities	1,424,730	114,172	88,698
Net (decrease) increase in cash and cash equivalents	(294,452)	370,941	98,403
Cash and cash equivalents at beginning of period	603,623	232,682	134,279
Cash and cash equivalents at end of period	$ 309,171	$ 603,623	$ 232,682