UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net income	$ 26,390	$ 53,111
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	61,759	57,029
Deferred taxes	4,989	4,272
Compensation expense related to share-based compensation plans	8,209	8,687
Loss (gain) on sale of assets	96	(1,526)
Donated equipment	5,626
Changes in operating assets and liabilities:
Restricted investments	1,640	(2,736)
Accounts receivable, net	(2,392)	55,089
Prepaid taxes	(83)	(422)
Prepaid expenses and other current assets	10,350	15,932
Other assets	(637)	(2,349)
Accounts payable	4,989	(38,391)
Accrued expenses	(9,440)	(14,620)
Non-current liabilities	21	1,187
Net cash provided by operating activities	111,517	135,263
Cash flows from investing activities:
Proceeds from sale of equipment	521	7,664
Purchases of property and equipment	(49,271)	(28,712)
Proceeds from the disposition of discontinued operations		19,439
Acquisition, net of cash acquired		(734)
Net cash used in investing activities	(48,750)	(2,343)
Cash flows from financing activities:
Purchase of treasury stock		(7,282)
Proceeds from issuance of debt	127,462	18,335
Repayments of long term debt	(150,282)	(51,324)
Stock withheld for payments of withholding taxes	(3,944)	(2,746)
Finance lease payments	(1,493)	(1,465)
Net cash used in financing activities	(28,257)	(44,482)
Effect of exchange rate changes on cash and cash equivalents	(66)	(10)
Net increase in cash and cash equivalents	34,444	88,428
Cash and cash equivalents beginning of the period	168,729	61,435
Cash and cash equivalents end of the period	203,173	149,863
Supplemental disclosures of cash paid for:
Interest	5,323	5,578
Income taxes	$ 822	$ 21,500