XML 61 R50.htm IDEA: XBRL DOCUMENT v3.10.0.1
UNCONSOLIDATED AFFILIATES (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]          
Equity in net earnings (loss) from investments $ 36,570 $ 39,363 $ 76,757 $ 78,927  
Accounts Payable, Related Parties, Current 12,300   12,300   $ 13,600
Income Statement [Abstract]          
Operating revenues 151,771 157,603 310,679 311,883  
Operating expenses 68,120 69,465 136,521 136,401  
Net income 77,913 92,072 162,393 173,203  
Distributions paid to us 48,424 49,760 98,240 96,680  
Unconsolidated Affiliates [Member]          
Schedule of Equity Method Investments [Line Items]          
Related Party Transaction, Expenses from Transactions with Related Parties 38,200 39,400 75,700 76,100  
Northern Border Pipeline          
Schedule of Equity Method Investments [Line Items]          
Equity in net earnings (loss) from investments 15,240 15,622 32,377 34,439  
Overland Pass Pipeline Company          
Schedule of Equity Method Investments [Line Items]          
Equity in net earnings (loss) from investments 16,246 14,884 32,633 28,450  
Roadrunner Gas Transmission          
Schedule of Equity Method Investments [Line Items]          
Equity in net earnings (loss) from investments 5,542 4,889 10,500 9,294  
Income Statement [Abstract]          
Payments to Acquire Equity Method Investments     0 4,000  
Other Unconsolidated Affiliates          
Schedule of Equity Method Investments [Line Items]          
Equity in net earnings (loss) from investments $ (458) $ 3,968 $ 1,247 $ 6,744