Quarterly report pursuant to Section 13 or 15(d)

Other Non-Current Assets - Equity Method Investments (Details)

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Other Non-Current Assets - Equity Method Investments (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2018
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2018
USD ($)
mi
Sep. 30, 2017
USD ($)
May 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Investment [Line Items]            
Equity method investment $ 92,000,000   $ 92,000,000     $ 64,000,000
Accounts receivable—related party 3,000,000   3,000,000     2,000,000
Midship Holdings [Member]            
Investment [Line Items]            
Equity method investment 84,000,000   84,000,000     55,000,000
O&M Services [Member] | Midship Pipeline [Member] | Service Agreements [Member]            
Investment [Line Items]            
Other—related party 4,000,000 $ 1,000,000 8,000,000 $ 2,000,000    
Accounts receivable—related party 3,000,000   $ 3,000,000     $ 2,000,000
CCL [Member] | Midship Pipeline [Member] | Natural Gas Transportation Agreement [Member]            
Investment [Line Items]            
Long-term Purchase Commitment, Period     10 years      
Midship Pipeline [Member]            
Investment [Line Items]            
Length Of Natural Gas Pipeline | mi     200      
Midship Pipeline [Member] | CCL [Member] | Midship Pipeline Letter of Credit [Member]            
Investment [Line Items]            
Letter of Credit, Maximum Borrowing Capacity         $ 16,000,000  
Letters of credit issued 0   $ 0      
EIG [Member] | Maximum [Member]            
Investment [Line Items]            
Investment Company, Financial Commitment to Investee, Future Amount $ 500,000,000   $ 500,000,000