Lease Agreements and Power Purchase Agreements - Minimum Future Rental Receipts on Operating Leases (Details) $ in Thousands	Aug. 31, 2015 USD ($)
Operating Leased Assets [Line Items]
Minimum future rentals on residential operating leases, 2015 (remaining three months)	$ 1,725
Minimum future rentals on residential operating leases, 2016	8,979
Minimum future rentals on residential operating leases, 2017	8,940
Minimum future rentals on residential operating leases, 2018	8,902
Minimum future rentals on residential operating leases, 2019	8,662
Minimum future rentals on residential operating leases, Thereafter	50,188
Minimum future rentals on residential operating leases, Total	87,396
Minimum future rentals on residential operating leases placed in service
Operating Leased Assets [Line Items]
Minimum future rentals on residential operating leases, 2015 (remaining three months)	921
Minimum future rentals on residential operating leases, 2016	3,690
Minimum future rentals on residential operating leases, 2017	3,709
Minimum future rentals on residential operating leases, 2018	3,729
Minimum future rentals on residential operating leases, 2019	3,750
Minimum future rentals on residential operating leases, Thereafter	50,188
Minimum future rentals on residential operating leases, Total	65,987
Maryland Solar Lease
Operating Leased Assets [Line Items]
Minimum future rentals on residential operating leases, 2015 (remaining three months)	804
Minimum future rentals on residential operating leases, 2016	5,289
Minimum future rentals on residential operating leases, 2017	5,231
Minimum future rentals on residential operating leases, 2018	5,173
Minimum future rentals on residential operating leases, 2019	4,912
Minimum future rentals on residential operating leases, Total	$ 21,409