CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net income	$ 73,171	$ 56,586
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	58,728	64,553
Stock-based compensation expense	1,730	1,218
Gain on sale of property and equipment	(6,198)	(7,017)
Unrealized loss on interest rate swap	3,856	4,854
Other non-cash items	4,125	240
Changes in assets and liabilities:
Accounts receivable	(91,741)	(177,942)
Contract assets	(16,783)	32,274
Other current assets	9,707	1,219
Other long-term assets	1,073	167
Accounts payable	16,533	(29,757)
Contract liabilities	63,682	(3,915)
Operating lease assets and liabilities, net	3,250	(1,489)
Accrued liabilities	36,394	17,662
Other long-term liabilities	33,952	1,231
Net cash provided by (used in) operating activities	191,479	(40,116)
Cash flows from investing activities:
Purchase of property and equipment	(54,404)	(78,255)
Proceeds from sale of property and equipment	17,710	24,393
Net cash used in investing activities	(36,694)	(53,862)
Cash flows from financing activities:
Borrowings under revolving line of credit		212,880
Payments on revolving line of credit		(212,880)
Proceeds from issuance of long-term debt	33,873	55,008
Repayment of long-term debt	(56,321)	(55,824)
Proceeds from issuance of common stock purchased under a long-term incentive plan	578	1,804
Payment of taxes on conversion of Restricted Stock Units	(548)	(1,519)
Cash distribution to noncontrolling interest holders	(1,000)	(3,505)
Repurchase of common stock	(10,959)
Dividends paid	(8,707)	(9,152)
Other	(2,888)	(328)
Net cash used in financing activities	(45,972)	(13,516)
Effect of exchange rate changes on cash and cash equivalents	(553)	268
Net change in cash and cash equivalents	108,260	(107,226)
Cash and cash equivalents at beginning of the year	120,286	151,063
Cash and cash equivalents at end of the year	228,546	43,837
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for interest	13,433	12,400
Cash paid for income taxes, net of refunds received	5,288	(1,421)
Leased assets obtained in exchange for new operating leases	51,664	118,755
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES
Dividends declared and not yet paid	$ 2,887	$ 3,059