Construction Contracts (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Capitalized contract cost, amortization	$ 300	$ 0
Construction receivables retentions	3,200		$ 8,500
Retention payable	1,789	$ 1,711	3,037	$ 3,591
Construction
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Retention payable	14,700		21,600
Portion Attributable To Pending Contracts
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Deferred pre-contract costs	$ 700		$ 1,400