Quarterly report pursuant to Section 13 or 15(d)

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

v3.7.0.1
Summary of Significant Accounting Policies - Sale-Leaseback (Details)
3 Months Ended
Mar. 31, 2017
USD ($)
project
Mar. 31, 2016
USD ($)
project
Mar. 31, 2015
USD ($)
Sale Leaseback Transaction [Line Items]      
Sale Price $ 8,783,000 $ 3,541,000  
Solar Photovoltaic Projects      
Sale Leaseback Transaction [Line Items]      
Maximum combined funding amount     $ 100,000,000
Number of Solar PV Projects Sold | project 2 2  
Sale Price $ 8,783,000 $ 3,541,000  
Deferred Gain Recorded 273,000 589,000  
Deferred Loss Recorded 913,000 0  
Capital Lease Asset/Liability Recorded $ 4,751,000 $ 1,509,000  
Initial Lease Term   20 years  
Percentage of fair value threshold, integral equipment 10.00%    
Net amortization expense $ 9,000 $ 23,000  
Solar Photovoltaic Projects | Minimum      
Sale Leaseback Transaction [Line Items]      
Initial Lease Term 10 years    
Lease Payment $ 4,000 8,000  
Solar Photovoltaic Projects | Maximum      
Sale Leaseback Transaction [Line Items]      
Initial Lease Term 20 years    
Lease Payment $ 407,000 $ 139,000