Construction Contracts - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Contractors [Abstract]
Deferred precontract costs	$ 1,400	$ 600
Amortization of pre-contract costs	100
Construction receivables retentions	8,500	9,900
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Retention payable	3,037	3,591
Construction
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Retention payable	$ 21,600	$ 17,400