Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Project Development Costs (Details)

v3.8.0.1
Summary of Significant Accounting Policies - Project Development Costs (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Accounting Policies [Abstract]    
Capitalized project development costs, noncurrent $ 1,401 $ 1,524