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 6 Months Ended
Jun. 30, 2018
USD ($)
project
Jun. 30, 2017
USD ($)
project
Jun. 30, 2018
USD ($)
project
Jun. 30, 2017
USD ($)
project
Dec. 31, 2017
USD ($)
Sep. 30, 2016
USD ($)
Sale Leaseback Transaction [Line Items]            
Number of Solar PV Projects Sold | project 0   0 1    
Sale Price     $ 0 $ 21,454,000    
Solar Photovoltaic Projects            
Sale Leaseback Transaction [Line Items]            
Maximum combined funding amount           $ 100,000,000
Number of Solar PV Projects Sold | project   4        
Sale Price   $ 12,671,000        
Deferred Gain Recorded $ 5,785,000 932,000 5,785,000 932,000 $ 6,173,000  
Deferred Loss Recorded 2,090,000 144,000 $ 2,090,000 144,000 $ 2,172,000  
Capital Lease Asset/Liability Recorded   $ 5,774,000   5,774,000    
Initial Lease Term   20 years        
Percentage of fair value threshold, integral equipment     10.00%      
Net amortization expense $ (46,000) $ (15,000) $ (105,000) $ (24,000)    
Solar Photovoltaic Projects | Minimum            
Sale Leaseback Transaction [Line Items]            
Lease Payment   4,000        
Solar Photovoltaic Projects | Maximum            
Sale Leaseback Transaction [Line Items]            
Lease Payment   $ 252,000