Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net income	$ 129,331	$ 84,734	$ 39,755
Adjustment to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	78,862	69,086	69,179
Amortization of contract acquisition costs	590	1,002	3,015
Amortization of debt issuance costs	732	1,083	992
Imputed interest expense and fair value adjustments to contingent consideration	4,484	2,339	10,217
Provision for credit losses	494	1,711	3,679
(Gain) loss on disposal of assets	521	189	111
Loss on dissolution of subsidiary	19,905	0	0
Impairment losses	5,809	3,735	1,452
Impairment of equity investment	0	0	15,632
Gain (adjustment) on bargain purchase of a business	0	0	(685)
Non-cash loss on assets held-for-sale	0	0	1,616
Deferred income taxes	(5,193)	(1,376)	(7,975)
Excess tax benefit from equity-based awards	(726)	(1,231)	(635)
Equity-based compensation expense	12,507	12,814	12,145
(Gain) loss on foreign currency derivatives	103	(140)	1,524
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	(40,625)	29,608	29,985
Prepaids and other assets	57,597	27,413	(30,438)
Accounts payable and accrued expenses	76,726	97,268	11,713
Deferred revenue and other liabilities	(69,197)	(90,246)	7,063
Net cash provided by operating activities	271,920	237,989	168,345
Cash flows from investing activities
Proceeds from sale of long-live assets	20	382	34
Purchases of property, plant and equipment	(59,772)	(60,776)	(43,450)
Investments in non-marketable equity investments	0	0	(2,119)
Acquisitions, net of cash acquired of $4,423, $4,547, and $4,530, respectively	(52,675)	(102,457)	(2,027)
Net cash used in investing activities	(112,427)	(162,851)	(47,562)
Cash flows from financing activities
Net proceeds (borrowings) from line of credit	95,000	8,000	(62,000)
Payments on other debt	(8,619)	(11,855)	(5,989)
Payments of contingent consideration and hold back payments to acquisitions	(48,686)	(5,902)	(1,349)
Dividends paid to shareholders	(134,554)	(28,739)	(25,346)
Payments to noncontrolling interest	(10,801)	(4,950)	(2,925)
Capital contribution from noncontrolling interest	0	3,362	0
Proceeds from exercise of stock options	0	0	208
Tax payments related to issuance of restricted stock units	(4,521)	(5,471)	(4,643)
Payments of debt issuance costs	(45)	(1,819)	(35)
Net cash (used in) provided by financing activities	(112,226)	(47,374)	(102,079)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	6,157	(410)	(14,904)
Increase (decrease) in cash, cash equivalents and restricted cash	53,424	27,354	3,800
Cash, cash equivalents and restricted cash, beginning of period	105,591	78,237	74,437
Cash, cash equivalents and restricted cash, end of period	159,015	105,591	78,237
Supplemental disclosures
Cash paid for interest	10,233	13,108	17,456
Cash paid for income taxes	47,761	36,316	39,984
Non-cash investing and financing activities
Acquisition of long lived assets through finance leases	1,852	3,731	15,018
Acquisition of equipment through increase in accounts payable, net	$ 347	$ 881	$ 339