Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 36,062	$ 43,107
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation	53,089	54,226
Amortization of intangible assets	7,391	4,805
Non-cash interest expense, net	725	453
Non-cash stock-based compensation expense	4,049	3,720
(Benefit from) provision for deferred income taxes	(12,614)	899
Equity in earnings of unconsolidated affiliates	(7,834)	(6,260)
Gains on sales of assets, net	(2,407)	(2,052)
Other non-cash items, net	734	(3,043)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable, net of allowance	48,337	(37,831)
Contract assets	26,311	6,376
Inventories	5,932	9,690
Other assets, current and long-term portion	17,906	2,398
Accounts payable and accrued expenses	34,058	(134,491)
Contract liabilities	2,603	3,821
Other liabilities, current and long-term portion	(11,076)	7,375
Net cash provided by (used in) operating activities	203,266	(46,807)
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	0	(93,684)
Capital expenditures	(60,594)	(34,396)
Proceeds from sale of property and equipment	8,363	8,654
Payments for other investments	(12,000)	(2,190)
Proceeds from other investments	648	10,413
Other investing activities, net	4,843	0
Net cash used in investing activities	(58,740)	(111,203)
Cash flows from financing activities:
Proceeds from credit facilities	675,935	866,397
Repayments of credit facilities	(671,780)	(670,794)
Repayments of other borrowings, net	0	(6)
Payments of finance lease obligations	(30,856)	(17,239)
Proceeds from stock-based awards	1,476	1,079
Payments for stock-based awards	(572)	(12)
Repurchases of common stock	(119,427)	(5,652)
Net cash (used in) provided by financing activities	(145,224)	173,773
Effect of currency translation on cash	934	9
Net increase in cash and cash equivalents	236	15,772
Cash and cash equivalents - beginning of period	71,427	27,422
Cash and cash equivalents - end of period	71,663	43,194
Supplemental cash flow information:
Interest paid	21,479	26,220
Income tax (refunds) payments, net	(287)	2,837
Supplemental disclosure of non-cash information:
Additions to property and equipment from finance leases	$ 26,932	$ 40,258