Quarterly report pursuant to Section 13 or 15(d)

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

v3.5.0.2
Summary of Significant Accounting Policies - Sale-Leaseback (Details)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2016
USD ($)
project
Mar. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Jun. 30, 2015
USD ($)
project
Mar. 31, 2015
USD ($)
project
Jun. 30, 2016
USD ($)
Jun. 30, 2015
USD ($)
Dec. 31, 2015
USD ($)
Sale Leaseback Transaction [Line Items]                
Proceeds from sale of solar-PV projects           $ 11,008,000 $ 7,581,000  
Solar Photovoltaic Projects                
Sale Leaseback Transaction [Line Items]                
Maximum combined funding amount         $ 50,000,000      
Number of solar photovoltaic projects sold | project 3     2 2      
Proceeds from sale of solar-PV projects $ 7,467,000 $ 3,541,000 $ 4,925,000 $ 7,581,000        
Percentage of fair value threshold, integral equipment           10.00%    
Sale leaseback transaction, deferred gain $ 708,000     1,029,000   $ 708,000 $ 1,029,000  
Lease terms 20 years   20 years     20 years 20 years  
Sale leaseback transaction, deferred loss $ 124,000   $ 1,421,000          
Capital lease liabilities             $ 3,511,000  
Solar Photovoltaic Projects | Minimum                
Sale Leaseback Transaction [Line Items]                
Monthly payments 8,000         $ 8,000   $ 7,000
Solar Photovoltaic Projects | Maximum                
Sale Leaseback Transaction [Line Items]                
Monthly payments 389,000         389,000   $ 348,000
Solar Photovoltaic Projects | Assets Held under Capital Leases                
Sale Leaseback Transaction [Line Items]                
Capital lease assets $ 4,266,000   $ 3,299,000 $ 0   $ 5,672,000