Construction Contract and Other Service Revenues - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Remaining performance obligations	$ 82,100,000		$ 82,100,000
Remaining performance obligation expected to be recognized during the remainder of year	21,000,000		21,000,000
Construction Contract Revenue
Disaggregation of Revenue [Line Items]
Performance obligations satisfied or already satisfied	84,000		158,000	$ 18,000
Deferred incremental costs incurred	$ 0	$ 0	$ 0	$ 0