Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities:
Net income	$ 28,139	$ 22,829
Adjustments for items not affecting cash:
Depreciation and amortization expenses	21,070	19,293
Stock-based compensation expense	7,193	2,973
Deferred income tax expense	963	1,331
Unrealized foreign exchange loss	459	782
Gain on disposition of property, plant and equipment	(68)	(47)
Amortization of debt issuance costs	720	756
Gain on disposition of equity investment		(1,700)
Amortization of right-of-use assets	3,172	3,343
Other, net	1,184	1,282
Net changes in operating assets and liabilities	117,855	(46,710)
Net cash provided by operating activities	180,687	4,132
Investing activities:
Property, plant and equipment additions	(1,556)	(3,495)
Proceeds on disposition of property, plant and equipment	66	333
Intangible asset additions	(8,769)	(7,220)
Issuance of loans receivable		(2,984)
Repayment of loans receivable	224	180
Distribution from equity investment		4,212
Proceeds on contingent consideration from equity investment		1,700
Net cash used in investing activities	(10,035)	(7,274)
Financing activities:
Share repurchase		(53,170)
Dividends paid to stockholders	(24,181)	(21,905)
Proceeds from exercise of options and share option plans	6,719	7,054
Payment of withholding taxes on issuance of shares	(7,542)	(2,984)
Net increase (decrease) in short-term debt	(2,886)	29,069
Repayment of long-term debt	(2,626)	(4,236)
Repayment of finance lease obligations	(2,629)	(2,189)
Net cash used in financing activities	(33,145)	(48,361)
Effect of changes in foreign currency rates on cash, cash equivalents, and restricted cash	(2,782)	(12,828)
Increase (decrease)	134,725	(64,331)
Beginning of period	306,895	420,256
Cash, cash equivalents, and restricted cash, end of period	$ 441,620	$ 355,925