Construction Contracts - Summary of Backlog (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue, Remaining Performance Obligation [Roll Forward]
Beginning backlog	$ 178,632	$ 37,921	$ 165,863	$ 49,167
New contracts/change orders	22,054	7,138	73,250	39,514
Work performed	(27,594)	(19,879)	(66,021)	(63,501)
Ending backlog	$ 173,092	$ 25,180	$ 173,092	$ 25,180
Minimum | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
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]: 2019-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected completion of contracts	18 months		18 months