Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies (Notes) (Details)

v3.8.0.1
Summary of Significant Accounting Policies (Notes) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2017
Dec. 15, 2014
Feb. 01, 2014
Convertible Notes          
Ownership interest (as a percent)     50.00%    
Convertible Notes          
Convertible Notes          
Face amount and over allotments       $ 172,500  
Interest rate (as a percent)     1.75% 1.75%  
Term Notes          
Convertible Notes          
Face amount and over allotments $ 142,000   $ 0    
ERS          
Convertible Notes          
Ownership interest (as a percent)         64.50%
Net loss attributable to noncontrolling interest $ 0 $ 0      
Klein | ERS          
Convertible Notes          
Ownership interest (as a percent) 80.80%   81.50%