Annual report pursuant to Section 13 and 15(d)

Leased Properties and Leases - Significant Leases (Details)

v3.8.0.1
Leased Properties and Leases - Significant Leases (Details)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Pinedale LGS [Member]      
Operating Leased Assets [Line Items]      
Percentage of total leased properties 39.90% 39.80%  
Percentage of leased property revenue 31.20% 30.40% 42.90%
Grand Isle Gathering System [Member]      
Operating Leased Assets [Line Items]      
Percentage of total leased properties 49.70% 50.00%  
Percentage of leased property revenue 59.10% 59.80% 42.30%
Portland Terminal Facility [Member]      
Operating Leased Assets [Line Items]      
Percentage of total leased properties 10.10% 9.90%  
Percentage of leased property revenue 9.60% 9.70% 13.30%