Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Sales Leaseback (Details)

v3.10.0.1
Summary of Significant Accounting Policies - Sales Leaseback (Details)
 1 Months Ended 12 Months Ended
Aug. 31, 2018
USD ($)
project
Dec. 31, 2018
USD ($)
project
Dec. 31, 2017
USD ($)
project
Dec. 31, 2016
USD ($)
project
Sep. 30, 2016
USD ($)
Sale Leaseback Transaction [Line Items]          
Capital lease assets, net   $ 6,985,000 $ 5,303,000    
Deferred Gain Recorded   6,153,000 6,173,000    
Deferred Loss Recorded   $ 2,032,000 $ 2,172,000    
Solar PV project          
Sale Leaseback Transaction [Line Items]          
Maximum combined funding amount $ 100,000,000       $ 100,000,000
Number of projects sold then leased back to separate investor | project 2   1    
Number of Solar PV Projects Sold | project   2 13 6  
Sale Price   $ 5,145,000 $ 51,204,000 $ 17,045,000  
Deferred Gain Recorded   574,000 4,625,000 906,000  
Deferred Loss Recorded   0 1,204,000 145,000  
Capital Lease Asset/Liability Recorded   $ 2,625,000 22,934,000 $ 8,830,000  
Percentage of fair value threshold integral equipment   10.00%      
Net amortization expense (gains)   $ 213,000 $ (79,000)    
Solar PV project | Minimum          
Sale Leaseback Transaction [Line Items]          
Initial Lease Term (years)     10 years 20 years  
Lease payment   $ 3,000 $ 4,000 $ 2,000  
Solar PV project | Maximum          
Sale Leaseback Transaction [Line Items]          
Initial Lease Term (years)   20 years 20 years 25 years  
Lease payment   $ 144,000 $ 510,000 $ 397,000