Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Deferred Revenue (Details)

v3.19.2
Summary of Significant Accounting Policies - Deferred Revenue (Details) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]      
Deferred revenue $ 703,431 $ 591,625 $ 564,900
Customer agreements      
Deferred Revenue Arrangement [Line Items]      
Deferred revenue 593,568 576,727  
Customer agreements | Payments received      
Deferred Revenue Arrangement [Line Items]      
Deferred revenue 552,227 538,926  
Customer agreements | Financing component balance      
Deferred Revenue Arrangement [Line Items]      
Deferred revenue 41,341 37,801  
SREC contracts      
Deferred Revenue Arrangement [Line Items]      
Deferred revenue 109,863 14,898  
SREC contracts | Payments received      
Deferred Revenue Arrangement [Line Items]      
Deferred revenue 107,279 12,977  
SREC contracts | Financing component balance      
Deferred Revenue Arrangement [Line Items]      
Deferred revenue $ 2,584 $ 1,921