Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net income	$ 48,158	$ 36,148
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	25,948	25,206
Amortization of intangibles	5,946	8,212
Amortization of deferred grants	(480)	(170)
Impairment losses	1,536	1,800
Unrealized foreign currency transaction (gains) losses, net	1,948	510
Stock-based compensation expense	8,369	3,902
Deferred income tax provision (benefit)	(846)	564
Net (gain) loss on lease termination	(1,670)
Bad debt expense (reversals)	236	1,129
Unrealized (gains) losses and premiums on financial instruments, net	(521)	665
(Earnings) losses from equity method investees	1,535	547
Other	1,011	(104)
Changes in assets and liabilities, net of acquisitions:
Receivables, net	(6,793)	294
Prepaid expenses	(1,364)	(239)
Other current assets	(1,097)	(263)
Deferred charges and other assets	(943)	238
Accounts payable	(4,702)	(4,184)
Income taxes receivable / payable	(3,481)	2,324
Accrued employee compensation and benefits	(6,731)	6,998
Other accrued expenses and current liabilities	6,241	(279)
Deferred revenue and customer liabilities	(938)	(1,666)
Other long-term liabilities	676	6,585
Operating lease assets and liabilities	(6,138)	(1,575)
Net cash provided by operating activities	65,900	86,642
Cash flows from investing activities:
Capital expenditures	(19,103)	(22,880)
Cash paid for business acquisitions, net of cash acquired	(165)
Purchase of intangible assets	(252)
Sale of intangible assets	200
Other	59	592
Net cash (used for) investing activities	(19,261)	(22,288)
Cash flows from financing activities:
Payments of long-term debt	(40,000)	(47,000)
Proceeds from issuance of long-term debt		23,000
Cash paid for repurchase of common stock		(35,928)
Taxes paid related to net share settlement of equity awards	(3,751)	(1,133)
Net cash (used for) financing activities	(43,751)	(61,061)
Effects of exchange rates on cash, cash equivalents and restricted cash	(2,819)	(1,795)
Net increase (decrease) in cash, cash equivalents and restricted cash	69	1,498
Cash, cash equivalents and restricted cash – beginning	104,396	129,185
Cash, cash equivalents and restricted cash – ending	104,465	130,683
Supplemental disclosures of cash flow information:
Cash paid for amounts included in the measurement of operating lease liabilities	35,307	31,484
Cash paid during period for interest	584	1,009
Cash paid during period for income taxes	17,457	8,947
Non-cash transactions:
Net right-of-use assets arising from new or remeasured operating lease liabilities	1,836	12,976
Capital expenditures incurred but not yet paid	9,187	4,978
Unrealized gain (loss) on postretirement obligation, net of taxes, in accumulated other comprehensive income (loss)		$ (44)
Property and equipment acquired under grant agreement	$ 2,136