Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Contract revenues	$ 159,767	$ 137,420	$ 296,610	$ 276,177
Costs of contract revenues	138,998	122,023	260,019	247,795
Gross profit	20,769	15,397	36,591	28,382
Selling, general and administrative expenses	16,864	17,528	31,878	32,507
(Gain) loss on sale of assets, net	(686)	335	(1,499)	(177)
Other gain from continuing operations	0	0	(5,448)	0
Operating income (loss) from operations	4,591	(2,466)	11,660	(3,948)
Other (expense) income
Other income	476	11	474	21
Interest income	47	0	47	0
Interest expense	(1,205)	(1,462)	(2,682)	(2,817)
Other expense, net	(682)	(1,451)	(2,161)	(2,796)
Income (loss) before income taxes	3,909	(3,917)	9,499	(6,744)
Income tax expense (benefit)	1,660	(1,624)	3,149	(2,643)
Net income (loss)	$ 2,249	$ (2,293)	$ 6,350	$ (4,101)
Basic (loss) income per share (in dollars per share)	$ 0.08	$ (0.08)	$ 0.22	$ (0.15)
Diluted (loss) income per share (in dollars per share)	$ 0.08	$ (0.08)	$ 0.22	$ (0.15)
Shares used to compute income (loss) per share:
Basic (in shares)	28,309,004	27,941,814	28,243,400	27,867,090
Diluted (in shares)	28,544,010	27,941,814	28,474,432	27,867,090