CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net income	$ 43,822	$ 26,390
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	64,033	61,759
Deferred taxes	4,428	4,989
Compensation expense related to share-based compensation plans	9,289	8,209
(Gain) loss on sale of assets	(4,033)	96
Other operating activities	0	5,626
Changes in operating assets and liabilities:
Restricted investments	48	1,640
Accounts receivable, net	(20,088)	(2,392)
Prepaid taxes	(395)	(83)
Prepaid expenses and other current assets	12,231	10,350
Other assets	(316)	(637)
Accounts payable	71,314	4,989
Accrued expenses	(1,652)	(9,440)
Non-current liabilities	(4,762)	21
Net cash provided by operating activities	173,919	111,517
Cash flows from investing activities:
Proceeds from sale of equipment	19,912	521
Purchases of property and equipment	(26,337)	(49,271)
Cash used in acquisition	(90)	0
Net cash used in investing activities	(6,515)	(48,750)
Cash flows from financing activities:
Proceeds from issuance of debt	17,464	127,462
Repayments of long-term debt	(57,854)	(150,282)
Stock withheld for payments of withholding taxes	(3,973)	(3,944)
Finance lease payments	(1,524)	(1,493)
Net cash used in financing activities	(45,887)	(28,257)
Effect of exchange rate changes on cash and cash equivalents	(2)	(66)
Net increase in cash and cash equivalents	121,515	34,444
Cash and cash equivalents beginning of the period	124,506	168,729
Cash and cash equivalents end of the period	246,021	203,173
Supplemental disclosures of cash paid for:
Interest	3,883	5,323
Income taxes	$ 11,375	$ 822