Annual report pursuant to Section 13 and 15(d)

Business Acquisitions and Related Transactions - Additional Information (Details)

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Business Acquisitions and Related Transactions - Additional Information (Details)
 1 Months Ended 12 Months Ended
Jan. 31, 2017
USD ($)
project
Dec. 31, 2016
USD ($)
Dec. 31, 2018
USD ($)
project
developer
Dec. 31, 2017
USD ($)
Dec. 30, 2018
USD ($)
Business Acquisition [Line Items]          
Loss on change in fair value     $ 44,000    
Measurement period adjustment, recorded as a reduction to goodwill       $ 2,639,000  
Number of developers current year solar projects were purchased from | developer     2    
Undisclosed Name of Acquiree One          
Business Acquisition [Line Items]          
Fair value of consideration     $ 2,326,000    
Initial cash payment     $ 1,901,000    
Contingent consideration, liability, acquired receivables, payment period     15 months    
Debt assumed     $ 0    
Measurement period adjustment, recorded as a reduction to goodwill     197,000    
Undisclosed Name of Acquiree Two          
Business Acquisition [Line Items]          
Initial cash payment     1,691,000    
Debt assumed     0    
Contingent consideration liabilities     $ 2,000,000    
Contingent consideration, liability, revenue targets, period     5 years    
Contingent consideration, liability, fair value     $ 599,000   $ 555,000
Solar PV project          
Business Acquisition [Line Items]          
Initial cash payment $ 2,409,000 $ 3,575,000      
Debt assumed $ 5,635,000 $ 9,503,000      
Number of projects acquired | project 2        
Solar Projects 2018          
Business Acquisition [Line Items]          
Fair value of consideration     72,921,000    
Initial cash payment     62,116,000    
Contingent consideration liabilities     $ 5,437,000    
Number of projects acquired | project     12    
Minimum          
Business Acquisition [Line Items]          
Intangible assets amortization period     1 year    
Maximum          
Business Acquisition [Line Items]          
Intangible assets amortization period     15 years    
Scenario, Plan          
Business Acquisition [Line Items]          
Number of projects acquired | project     6    
Scenario, Plan | Solar Projects 2018          
Business Acquisition [Line Items]          
Number of projects acquired | project     6