Consolidated Statement of Cash Flows (Statement) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 126,521	$ 103,096	$ 142,112
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	36,117	32,160	29,200
Bad debt (recovery) allowance	(1,000)	862	2,393
Deferred income taxes	16,246	732	(60,060)
Deferred compensation plan activity	3,706	3,994	4,323
Stock-based compensation expense	32,114	8,091	7,882
Amortization and write-off of deferred debt issuance costs	985	553	552
Change in fair value of derivative	(347)	159	487
Change in fair value of contingent consideration	(1,340)	62	272
Foreign currency remeasurement (gain) loss	(24,502)	5,311	(1,645)
Loss from investment accounted for using the equity method, net of tax	2,474	1,275	0
Changes in assets and liabilities, net of effect from acquisitions:
Accounts receivable	12,388	(21,152)	(41,787)
Prepaid and other assets	11,705	(668)	2,831
Accounts payable, accruals and other liabilities	47,656	41,880	37,249
Deferred revenues	(565)	(268)	21,247
Income taxes payable	(3,818)	(5,314)	16,409
Net cash provided by operating activities	258,340	170,773	161,465
Cash flows from investing activities:
Purchases of property and equipment and investment in capitalized software	(15,496)	(15,804)	(18,616)
Capitalization of costs to translate software products into foreign languages	(951)	(835)	(877)
Acquisitions, net of cash acquired of $5,266, $2,523, and $7,774, respectively	(93,032)	(34,054)	(135,264)
Other investing activities	(7,854)	(3,000)	0
Net cash used in investing activities	(117,333)	(53,693)	(154,757)
Cash flows from financing activities:
Proceeds from credit facilities	550,875	191,250	148,250
Payments of credit facilities	(538,625)	(216,250)	(159,500)
Proceeds from term loan	125,000	0	0
Repayment of term loan	(125,000)	0	0
Payments of debt issuance costs	(432)	0	0
Payments of financing leases	(189)	0	0
Payments of acquisition debt and other consideration	(3,425)	(11,029)
Payments of acquisition debt and other consideration			9
Payments of Class B Common Stock follow-on offering expenses	(1,373)	0	0
Payments of dividends	(422,646)	(24,989)	(20,059)
Payments for shares acquired including shares withheld for taxes	(83,975)	(24,166)	(46,451)
Proceeds from exercise of stock options	9,128	3,626	2,732
Net cash used in financing activities	(136,511)	(77,048)	(58,799)
Effect of exchange rate changes on cash and cash equivalents	(3,591)	(114)	(1,193)
Increase (decrease) in cash and cash equivalents	905	39,918	(53,284)
Cash and cash equivalents, beginning of year	121,101	81,183	134,467
Cash and cash equivalents, end of year	122,006	121,101	81,183
Supplemental information:
Cash paid for income taxes	28,986	27,907	25,782
Income tax refunds	3,863	1,752	7,285
Interest paid	8,012	9,221	8,863
Non-cash contingent acquisition consideration	2,380	4,498	13,456
Non-cash deferred, non-contingent consideration, net	1,416	0	690
Private Placement
Cash flows from financing activities:
Proceeds from issuance of common stock	58,349	4,510	16,220
Follow-On Offering
Cash flows from financing activities:
Proceeds from issuance of common stock	$ 295,802	$ 0	$ 0