Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Sale-Leaseback (Details)

v3.10.0.1
Summary of Significant Accounting Policies - Sale-Leaseback (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2018
USD ($)
project
Sep. 30, 2017
USD ($)
project
Sep. 30, 2018
USD ($)
project
Sep. 30, 2017
USD ($)
project
Sep. 30, 2016
USD ($)
Sale Leaseback Transaction [Line Items]          
Sale Price     $ 5,145,000 $ 30,611,000  
Net amortization expense $ (48,000) $ (25,000) (153,000) $ (49,000)  
Solar Photovoltaic Projects          
Sale Leaseback Transaction [Line Items]          
Maximum combined funding amount $ 100,000   $ 100,000   $ 100,000,000
Number of Solar PV Projects Sold | project 2 3 2 1  
Sale Price $ 5,145,000 $ 9,157,000      
Deferred Gain Recorded 611,000 642,000      
Deferred Loss Recorded 0 0      
Capital Lease Asset/Liability Recorded $ 2,591,000 $ 4,114,000 $ 2,591,000 $ 4,114,000  
Initial Lease Term 20 years 20 years      
Percentage of fair value threshold, integral equipment     10.00%    
Solar Photovoltaic Projects | Minimum          
Sale Leaseback Transaction [Line Items]          
Lease Payment $ 1,000 $ 13,000      
Solar Photovoltaic Projects | Maximum          
Sale Leaseback Transaction [Line Items]          
Lease Payment $ 738,000 $ 231,000