Quarterly report pursuant to Section 13 or 15(d)

Indebtedness - Schedule of Debt (Details)

v3.10.0.1
Indebtedness - Schedule of Debt (Details) - USD ($)
$ in Thousands
Sep. 30, 2018
Dec. 31, 2017
Debt Instrument [Line Items]    
Long term debt, current $ 27,496 $ 21,529
Long term debt, noncurrent 1,537,102 1,273,416
Long term debt 1,564,598 1,294,945
Unused borrowing capacity $ 406 $ 13,191
Bank line of credit | Minimum    
Debt Instrument [Line Items]    
Interest rate 5.33% 4.58%
Bank line of credit | Maximum    
Debt Instrument [Line Items]    
Interest rate 5.54% 4.87%
Senior | Minimum    
Debt Instrument [Line Items]    
Interest rate 4.33% 3.63%
Senior | Maximum    
Debt Instrument [Line Items]    
Interest rate 5.39% 4.69%
Subordinated    
Debt Instrument [Line Items]    
Unused borrowing capacity $ 0 $ 27
Subordinated | Minimum    
Debt Instrument [Line Items]    
Interest rate 7.03% 6.36%
Subordinated | Maximum    
Debt Instrument [Line Items]    
Interest rate 7.84% 7.13%
Recourse debt    
Debt Instrument [Line Items]    
Long term debt, current $ 0 $ 0
Long term debt, noncurrent 247,000 247,000
Long term debt 247,000 247,000
Unused borrowing capacity 406 406
Recourse debt | Bank line of credit    
Debt Instrument [Line Items]    
Long term debt, current 0 0
Long term debt, noncurrent 247,000 247,000
Long term debt 247,000 247,000
Unused borrowing capacity 406 406
Non-recourse debt    
Debt Instrument [Line Items]    
Long term debt, current 27,496 21,529
Long term debt, noncurrent 1,290,102 1,026,416
Long term debt 1,317,598 1,047,945
Unused borrowing capacity 0 12,785
Non-recourse debt | Senior    
Debt Instrument [Line Items]    
Long term debt, current 18,693 3,561
Long term debt, noncurrent 1,049,254 804,894
Long term debt 1,067,947 808,455
Unused borrowing capacity 0 12,758
Non-recourse debt | Subordinated    
Debt Instrument [Line Items]    
Long term debt, current 4,641 4,301
Long term debt, noncurrent 153,302 107,187
Long term debt 157,943 111,488
Non-recourse debt | Securitization Class A    
Debt Instrument [Line Items]    
Long term debt, current 3,703 3,534
Long term debt, noncurrent 78,241 82,203
Long term debt 81,944 85,737
Unused borrowing capacity $ 0 $ 0
Interest rate 4.40% 4.40%
Non-recourse debt | Securitization Class B    
Debt Instrument [Line Items]    
Long term debt, current $ 459 $ 440
Long term debt, noncurrent 9,305 9,644
Long term debt 9,764 10,084
Unused borrowing capacity $ 0 $ 0
Interest rate 5.38% 5.38%
Non-recourse debt | SREC Loans    
Debt Instrument [Line Items]    
Long term debt, current   $ 9,693
Long term debt, noncurrent   22,488
Long term debt   32,181
Unused borrowing capacity   $ 0
Interest rate   7.28%