XML 93 R69.htm IDEA: XBRL DOCUMENT v3.8.0.1
Other Intangible Assets (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Other Intangible Assets [Line Items]      
Accumulated amortization $ (12,138) $ (11,075)  
Intangible assets, gross 28,055 25,495  
Intangible assets, net 15,917 14,420  
Rights-of-Way      
Other Intangible Assets [Line Items]      
Rights-of-way assets $ 15,828 $ 13,268  
Supply contracts      
Other Intangible Assets [Line Items]      
Estimated useful life (years) 11 years 6 months 11 years 6 months  
Intangible assets, gross $ 12,227 $ 12,227  
Accumulated amortization (12,138) (11,075)  
Intangible assets, net 89 1,152  
Amortization expense 1,100 $ 1,100 $ 1,100
Estimated future amortization expense $ 100