Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Revenue, Major Customer [Line Items]
Costs and estimated earnings in excess of billings on uncompleted contracts	$ 9,217				$ 46,006				$ 9,217	$ 46,006		$ 47,389
Billings in excess of costs and estimated earnings on uncompleted contracts	21,761				33,923				21,761	33,923		35,668
Deferred income taxes	49				13,243				49	13,243		13,167
Retained earnings	(31,861)				62,847				(31,861)	62,847		62,561
Contract revenues	99,211	$ 125,073	$ 159,767	$ 136,843	162,214	$ 140,162	$ 137,420	$ 138,757	520,894	578,553	$ 578,236
Costs of contract revenues									499,245	511,663	510,754
Gross profit	$ (20,880)	$ 5,938	$ 20,769	$ 15,822	$ 27,751	$ 10,757	$ 15,397	$ 12,985	21,649	66,890	67,482
Income tax (benefit) expense									(12,233)	(4,541)	1,581
Net (loss) income									$ (94,422)	$ 400	$ (3,620)
Basic income (loss) per share (USD per share)	$ (3.32)	$ (0.22)	$ 0.08	$ 0.15	$ 0.34	$ (0.18)	$ (0.08)	$ (0.07)	$ (3.31)	$ 0.01	$ (0.13)
Diluted income (loss) per share (USD per share)	$ (3.32)	$ (0.22)	$ 0.08	$ 0.14	$ 0.34	$ (0.18)	$ (0.08)	$ (0.07)	$ (3.31)	$ 0.01	$ (0.13)
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				$ 46,006				$ 10,040	$ 46,006
Billings in excess of costs and estimated earnings on uncompleted contracts	22,886				33,923				22,886	33,923
Deferred income taxes	(57)				13,243				(57)	13,243
Retained earnings	(32,057)				$ 62,847				(32,057)	$ 62,847
Contract revenues									519,769
Costs of contract revenues									498,422
Gross profit									21,347
Income tax (benefit) expense									(12,339)
Net (loss) income									$ (94,618)
Basic income (loss) per share (USD per share)									$ (3.32)
Diluted income (loss) per share (USD per share)									$ (3.32)
Accounting Standards Update 2014-09 | 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 taxes	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 income (loss) per share (USD per share)									$ 0.01
Diluted income (loss) per share (USD per share)									$ 0.01
Costs And Estimated Earnings In Excess Of Billings On Uncompleted Contracts
Revenue, Major Customer [Line Items]
Contract with customer, liability, revenue recognized									$ 1,100