Annual report pursuant to Section 13 and 15(d)

Business Segment Information - Revenue (Details)

v3.8.0.1
Business Segment Information - Revenue (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Revenue from External Customer [Line Items]                      
Revenues $ 211,133 $ 204,744 $ 166,665 $ 134,610 $ 174,225 $ 180,598 $ 162,628 $ 133,776 $ 717,152 $ 651,227 $ 630,832
Project                      
Revenue from External Customer [Line Items]                      
Revenues                 506,550 454,200 434,380
Energy Assets                      
Revenue from External Customer [Line Items]                      
Revenues                 69,241 64,882 55,130
Operations and Maintenance                      
Revenue from External Customer [Line Items]                      
Revenues                 60,574 63,082 59,117
Integrated-PV                      
Revenue from External Customer [Line Items]                      
Revenues                 38,796 29,325 40,070
Other services                      
Revenue from External Customer [Line Items]                      
Revenues                 $ 41,991 $ 39,738 $ 42,135