CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Cash flows from operating activities
Net income (loss)	$ (28,729)	$ 34,466	$ (325,280)	$ 30,148
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization			43,051	44,061
Deferred income taxes			20,428	5,261
(Income) loss from discontinued operations	989	141	1,822	(32)
Restructuring charges	11,259	1,702	12,370	6,845
Legal settlement				8,500
Impairment charges			203,076
Gains on dispositions of property and other assets			(14,935)	(938)
Share-based compensation expense	1,937	1,831	649	6,448
Multi-employer pension plan withdrawal			462	15,508
Other non-cash items, net			10,371	2,772
Change in operating assets and liabilities:
Receivables			104,722	(37,028)
Inventories			833	389
Current contract costs			16,418	(13,929)
Accounts payable			(76,355)	20,121
Restructuring liabilities			(4,606)	(5,012)
Accrued compensation			(25,268)	2,308
Contract liabilities			(32,650)	29,177
Income taxes payable			1,290	3,777
Other assets and liabilities, net			17,696	(17,236)
Net cash (used in) provided by operating activities			(45,906)	101,140
Cash flows from investing activities
Capital expenditures			(40,057)	(60,868)
Cash surrender value of life insurance policies			24,767
Cash paid for acquisitions, net				(90,992)
Proceeds from dispositions of property and other assets			21,788	1,022
Net cash provided by (used in) investing activities			6,498	(150,838)
Cash flows from financing activities
Proceeds from borrowings			191,733	170,459
Payments on debt and finance lease obligations			(273,663)	(99,340)
Dividends paid on common stock			(4,064)	(6,060)
Distributions to noncontrolling interest			(1,526)
Debt issuance costs			(1,585)
Payment of payroll taxes on stock-based compensation through shares withheld or repurchased			(1,062)	(3,019)
Common stock purchased for treasury			(2,785)
Proceeds from issuance of Convertible Series A Preferred Stock, net of issuance costs			125,763
Proceeds from exercise of stock options			2,077	92
Net cash provided by financing activities			34,888	62,132
Effect of exchange rate changes on cash and cash equivalents			(1,027)	(689)
Net change in cash and cash equivalents			(5,547)	11,745
Cash and cash equivalents, beginning of year			61,999	44,893	$ 44,893
Cash and cash equivalents, end of period	$ 56,452	$ 56,638	$ 56,452	$ 56,638	$ 61,999