CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net income	$ 190,349	$ 43,822
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	71,922	64,033
Deferred taxes	3,279	4,428
Compensation expense related to share-based compensation plans	10,237	9,289
Gain on sale of assets	(12,509)	(4,033)
Changes in operating assets and liabilities:
Restricted investments	5,200	48
Accounts receivable, net	(93,767)	(20,088)
Prepaid taxes	(2,166)	(395)
Prepaid expenses and other current assets	9,664	12,231
Other assets	(2,517)	(316)
Accounts payable	3,380	71,314
Accrued expenses	23,251	(1,652)
Non-current liabilities	(5,588)	(4,762)
Net cash provided by operating activities	200,735	173,919
Cash flows from investing activities:
Proceeds from sale of equipment	18,584	19,912
Purchases of property and equipment	(85,942)	(26,337)
Cash used in acquisition	0	(90)
Net cash used in investing activities	(67,358)	(6,515)
Cash flows from financing activities:
Proceeds from issuance of debt	66,194	17,464
Repayments of long-term debt	(54,114)	(57,854)
Stock withheld for payments of withholding taxes	(5,715)	(3,973)
Finance lease payments	(1,059)	(1,524)
Net cash provided by (used) in financing activities	5,306	(45,887)
Effect of exchange rate changes on cash and cash equivalent	9	(2)
Net increase in cash and cash equivalents	138,692	121,515
Cash and cash equivalents beginning of the period	159,784	124,506
Cash and cash equivalents end of the period	298,476	246,021
Supplemental disclosures of cash paid for:
Interest	3,710	3,883
Income taxes	$ 58,082	$ 11,375