Construction Contracts - Summary of Backlog (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue, Remaining Performance Obligation [Roll Forward]
Beginning backlog	$ 235,642	$ 160,871	$ 242,622	$ 165,863
New contracts/change orders	15,490	39,177	55,930	51,196
Work performed	(57,390)	(21,416)	(104,810)	(38,427)
Ending backlog	$ 193,742	$ 178,632	$ 193,742	$ 178,632
Minimum | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected completion of contracts	12 months		12 months
Maximum | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected completion of contracts	18 months		18 months