Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net income (loss)	$ 20,220	$ (5,359)	$ (94,422)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	23,893	26,096	31,799
Amortization of ROU operating leases	5,874	5,177
Amortization of ROU finance leases	3,324	2,312
Write-off of debt issuance costs upon debt modification	0	399	2,164
Amortization of deferred debt issuance costs	763	453	725
Deferred income taxes	17	71	(13,194)
Stock-based compensation	1,998	2,753	2,238
Gain on disposal of assets	(6,185)	(1,804)	(3,306)
Gain on involuntary disposition of assets, net	(2,859)
Goodwill impairment charges		0	69,483
Allowance for credit losses	(487)	0	4,280
Other gain from continuing operations	0	0	(5,448)
Change in operating assets and liabilities:
Accounts receivable	23,587	(51,709)	10,936
Income tax receivable	543	(495)	(128)
Inventory	148	503	647
Prepaid expenses and other	(1,070)	131	1,671
Costs and estimated earnings in excess of billings on uncompleted contracts	9,118	(32,172)	36,789
Accounts payable	(22,015)	28,894	(4,584)
Accrued liabilities	11,092	1,334	(5,301)
Operating lease liabilities	(5,399)	(5,843)
Income tax payable	(884)	1,523	(256)
Billings in excess of costs and estimated earnings on uncompleted contracts	(15,646)	27,020	(12,162)
Net cash provided by (used in) operating activities	46,032	(716)	21,931
Cash flows from investing activities:
Proceeds from sale of property and equipment	5,944	2,015	3,234
Purchase of property and equipment	(14,694)	(17,199)	(17,714)
Contributions to CSV life insurance	(99)	(721)	(260)
Proceeds from return of investment			94
Insurance claim proceeds related to property and equipment	5,720	2,574	1,346
Net cash used in investing activities	(3,129)	(13,331)	(13,300)
Cash flows from financing activities:
Borrowings from Credit Facility	10,000	63,000	39,861
Payments made on borrowings from Credit Facility	(48,204)	(70,210)	(48,111)
Proceeds from sale-leaseback arrangement		18,210
Loan costs from Credit Facility	(389)	(1,680)	(861)
Capital lease liability			(2,737)
Payments of finance lease liabilities	(3,619)	(2,906)
Purchase of vested stock-based awards	(188)
Exercise of stock options		35	2,815
Net cash (used in) provided by financing activities	(42,400)	6,449	(9,033)
Net change in cash and cash equivalents	503	(7,598)	(402)
Cash and cash equivalents at beginning of period	1,086	8,684	9,086
Cash and cash equivalents at end of period	1,589	1,086	8,684
Supplemental disclosures of cash flow information, cash paid during the period for:
Interest	3,187	6,311	4,819
Taxes, net of refunds	$ 2,174	$ 578	903
Non-cash investing activity
Capital lease expenditures included in accrued expenses			$ 13,103