Construction Contracts in Progress - Summary of Contracts in Progress (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Summary of Contracts in Progress [Abstract]
Costs incurred on uncompleted contracts	$ 101,600	$ 111,925
Estimated earnings	49,561	55,527
Earned revenue	151,161	167,452
Less billings to date	(145,670)	(162,427)
Total	5,491	5,025
Classified as follows:
Costs and estimated earnings in excess of billings on uncompleted contracts	7,894	6,755
Billings in excess of costs and estimated earnings on uncompleted contracts	$ (2,403)	$ (1,730)