Revenue from Contracts with Customers - Future Fixed Revenue from Stewardship and Real Estate Development Services (Details) $ in Thousands	Sep. 30, 2020 USD ($)
Revenue from Contract with Customer [Abstract]
Total Remaining Unsatisfied Performance Obligations	$ 14,746
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue from Contract with Customer [Abstract]
Total Remaining Unsatisfied Performance Obligations	$ 3,038
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction, period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue from Contract with Customer [Abstract]
Total Remaining Unsatisfied Performance Obligations	$ 6,575
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue from Contract with Customer [Abstract]
Total Remaining Unsatisfied Performance Obligations	$ 2,621
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue from Contract with Customer [Abstract]
Total Remaining Unsatisfied Performance Obligations	$ 2,512
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction, period