Accounting Standards - Effects of Adoption of ASC 606 and ASC 842 on Condensed Consolidated Statement of Operations (Details) - USD ($)	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	$ 163,856,000			$ 148,119,000			$ 437,813,000	$ 414,469,000
Cost of revenue	139,685,000			129,746,000			375,083,000	358,778,000
Gross profit	24,171,000			18,373,000			62,730,000	55,691,000
Selling, general and administrative expenses	17,045,000			16,568,000			47,596,000	49,691,000
Amortization of intangibles	109,000			149,000			526,000	499,000
Total operating expenses	17,154,000			16,717,000			48,122,000	50,190,000
Operating income	7,017,000			1,656,000			14,608,000	5,501,000
Interest expense, net	(2,154,000)			(1,759,000)			(6,449,000)	(4,190,000)
Gain on disposition of property and equipment	3,000			17,000			18,000	38,000
Loss on debt extinguishment	0			0			0	(513,000)
Gain on change in fair value of warrant liability	(1,371,000)			525,000			(1,312,000)	422,000
Impairment of goodwill	0			(4,359,000)			0	(4,359,000)
Total unallocated amounts				(5,576,000)				(8,602,000)
Income (loss) before income taxes	3,495,000			(3,920,000)			6,865,000	(3,101,000)
Income tax provision (benefit)	970,000			(942,000)			1,445,000	(681,000)
Net income (loss)	2,525,000	$ 2,947,000	$ (52,000)	(2,978,000)	$ (1,289,000)	$ 1,847,000	5,420,000	(2,420,000)
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				0				0
Cost of revenue				0				0
Gross profit				0				0
Selling, general and administrative expenses				0				0
Amortization of intangibles				0				0
Total operating expenses				0				0
Operating income				0				0
Interest expense, net				0				0
Gain on disposition of property and equipment				0				0
Loss on debt extinguishment								0
Gain on change in fair value of warrant liability				0
Impairment of goodwill				0				0
Total unallocated amounts				0				0
Income (loss) before income taxes				0				0
Income tax provision (benefit)				0				0
Net income (loss)				0				0
Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				118,424,000				327,643,000
Cost of revenue				107,281,000				292,901,000
Impairment of goodwill	0			(4,359,000)			0	(4,359,000)
Construction | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				0				0
Cost of revenue				0				0
Service
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				29,695,000				86,826,000
Cost of revenue				22,465,000				65,877,000
Total unallocated amounts	$ (3,522,000)			(1,217,000)			$ (7,743,000)	(4,243,000)
Service | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				0				0
Cost of revenue				0				0
Calculated under Revenue Guidance in Effect before Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				147,768,000				414,472,000
Cost of revenue				129,977,000				359,247,000
Gross profit				17,791,000				55,225,000
Selling, general and administrative expenses				16,568,000				49,691,000
Amortization of intangibles				149,000				499,000
Total operating expenses				16,717,000				50,190,000
Operating income				1,074,000				5,035,000
Interest expense, net				(1,759,000)				(4,190,000)
Gain on disposition of property and equipment				17,000				38,000
Loss on debt extinguishment								(513,000)
Gain on change in fair value of warrant liability				525,000				422,000
Impairment of goodwill				(4,359,000)				(4,359,000)
Total unallocated amounts				(5,576,000)				(8,602,000)
Income (loss) before income taxes				(4,502,000)				(3,567,000)
Income tax provision (benefit)				(1,090,000)				(797,000)
Net income (loss)				(3,412,000)				(2,770,000)
Calculated under Revenue Guidance in Effect before Topic 606 | Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				118,076,000				327,675,000
Cost of revenue				107,474,000				293,338,000
Calculated under Revenue Guidance in Effect before Topic 606 | Service
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				29,692,000				86,797,000
Cost of revenue				22,503,000				65,909,000
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				351,000				(3,000)
Cost of revenue				(231,000)				(469,000)
Gross profit				582,000				466,000
Selling, general and administrative expenses				0				0
Amortization of intangibles				0				0
Total operating expenses				0				0
Operating income				582,000				466,000
Interest expense, net				0				0
Gain on disposition of property and equipment				0				0
Loss on debt extinguishment								0
Gain on change in fair value of warrant liability				0
Impairment of goodwill				0				0
Total unallocated amounts				0				0
Income (loss) before income taxes				582,000				466,000
Income tax provision (benefit)				148,000				116,000
Net income (loss)				434,000				350,000
Difference between Revenue Guidance in Effect before and after Topic 606 | Construction | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				348,000				(32,000)
Cost of revenue				(193,000)				(437,000)
Difference between Revenue Guidance in Effect before and after Topic 606 | Service | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				3,000				29,000
Cost of revenue				$ (38,000)				$ (32,000)