Construction Contracts - Summary of Backlog (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue, Remaining Performance Obligation [Roll Forward]
Beginning backlog	$ 193,742	$ 178,632	$ 242,622	$ 165,863
New contracts/change orders	(12,461)	22,054	43,469	73,250
Work performed	(58,590)	(27,594)	(163,400)	(66,021)
Ending backlog	$ 122,691	$ 173,092	$ 122,691	$ 173,092
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