Operating Segments - Segment Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenue	$ 568,209,000	$ 553,334,000
Gross profit	81,386,000	71,877,000
Selling, general and administrative	63,601,000	63,168,000
Amortization of intangibles	630,000	642,000
Operating income	17,155,000	8,067,000
Impairment of goodwill	0	(4,359,000)
Interest income (expense), net	(8,627,000)	(6,285,000)
Loss on debt extinguishment	0	(513,000)
Gain (loss) on change in fair value of warrant liability	(1,634,000)	588,000
Gain on embedded derivative	0	388,000
Gain on sale of property and equipment	95,000	57,000
Total unallocated amounts	(10,166,000)	(5,765,000)
Income (loss) before income taxes	6,989,000	(2,057,000)
Depreciation and amortization	6,171,000	6,286,000
Construction
Segment Reporting Information [Line Items]
Impairment of goodwill	0	(4,359,000)
Service
Segment Reporting Information [Line Items]
Impairment of goodwill	0	0
Operating Segments | Construction
Segment Reporting Information [Line Items]
Revenue	440,979,000	438,196,000
Gross profit	45,115,000	43,493,000
Selling, general and administrative	37,708,000	40,357,000
Depreciation and amortization	4,187,000	4,434,000
Operating Segments | Service
Segment Reporting Information [Line Items]
Revenue	127,230,000	115,138,000
Gross profit	36,271,000	28,384,000
Selling, general and administrative	24,825,000	21,045,000
Depreciation and amortization	1,354,000	1,210,000
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Selling, general and administrative	1,068,000	1,766,000
Depreciation and amortization	$ 630,000	$ 642,000