Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2017
Revenue, Major Customer [Line Items]
Costs and estimated earnings in excess of billings on uncompleted contracts	$ 41,389				$ 9,217				$ 41,389	$ 9,217	$ 46,006	$ 47,389
Billings in excess of costs and estimated earnings on uncompleted contracts	48,781				21,761				48,781	21,761	33,923	35,668
Deferred income tax liability	205				49				205	49	13,243	13,167
Retained earnings	(37,220)				(31,861)				(37,220)	(31,861)	62,847	62,561
Contract revenues	199,793	$ 199,507	$ 165,985	$ 143,105	99,211	$ 125,073	$ 159,767	$ 136,843	708,390	520,894	578,553
Costs of contract revenues									644,349	504,118	516,313
Gross profit	19,089	20,893	14,977	9,082	(22,206)	4,825	19,462	14,695	64,041	16,776	62,240
Income tax (benefit) expense									1,868	(12,233)	(4,541)
Net (loss) income	$ 159	$ 4,039	$ (1,633)	$ (7,924)	$ (94,416)	$ (6,356)	$ 2,249	$ 4,101	$ (5,359)	$ (94,422)	$ 400
Basic (loss) income per share (in dollars per share)	$ 0.01	$ 0.14	$ (0.06)	$ (0.27)	$ (3.32)	$ (0.22)	$ 0.08	$ 0.15	$ (0.18)	$ (3.31)	$ 0.01
Diluted (loss) income per share (in dollars per share)	$ 0.01	$ 0.14	$ (0.06)	$ (0.27)	$ (3.32)	$ (0.22)	$ 0.08	$ 0.14	$ (0.18)	$ (3.31)	$ 0.01
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Major Customer [Line Items]
Costs and estimated earnings in excess of billings on uncompleted contracts					$ 10,040					$ 10,040
Billings in excess of costs and estimated earnings on uncompleted contracts					22,886					22,886
Deferred income tax asset					(57)					(57)
Retained earnings					(32,057)					(32,057)
Contract revenues										519,769
Costs of contract revenues										503,295
Gross profit										16,474
Income tax (benefit) expense										(12,339)
Net (loss) income										$ (94,618)
Basic (loss) income per share (in dollars per share)										$ (3.32)
Diluted (loss) income per share (in dollars per share)										$ (3.32)
Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Major Customer [Line Items]
Costs and estimated earnings in excess of billings on uncompleted contracts					(823)					$ (823)		1,383
Billings in excess of costs and estimated earnings on uncompleted contracts					(1,125)					(1,125)		1,745
Deferred income tax liability					106					106		(76)
Retained earnings					$ 196					196		$ (286)
Contract revenues										1,125
Costs of contract revenues										823
Gross profit										302
Income tax (benefit) expense										106
Net (loss) income										$ 196
Basic (loss) income per share (in dollars per share)										$ 0.01
Diluted (loss) income per share (in dollars per share)										$ 0.01