Quarterly report pursuant to Section 13 or 15(d)

Leased Properties and Leases - Significant Leases (Details)

v3.10.0.1
Leased Properties and Leases - Significant Leases (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Pinedale LGS [Member]          
Operating Leased Assets [Line Items]          
Percentage of total leased properties 39.90%   39.90%   39.90%
Percentage of leased property revenue 35.70% 31.10% 34.60% 30.80%  
Variable rent $ 1.2 $ 0.1 $ 2.8 $ 0.1  
Grand Isle Gathering System [Member]          
Operating Leased Assets [Line Items]          
Percentage of total leased properties 49.60%   49.60%   49.70%
Percentage of leased property revenue 55.30% 59.20% 56.20% 59.50%  
Portland Terminal Facility [Member]          
Operating Leased Assets [Line Items]          
Percentage of total leased properties 10.20%   10.20%   10.10%
Percentage of leased property revenue 8.90% 9.50% 9.10% 9.60%