Construction Contracts (Summary of Backlog) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue, Remaining Performance Obligation [Roll Forward]
Beginning backlog	$ 242,622	$ 165,863	$ 49,167
New contracts/change orders	45,882	182,495	192,852
Work performed	(217,246)	(105,736)	(76,156)
Ending backlog	$ 71,258	$ 242,622	$ 165,863
Minimum | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected completion of contracts	12 months
Maximum | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected completion of contracts	18 months