Transactions with Affiliates (Notes)	6 Months Ended
Jun. 30, 2018
Related Party Transactions [Abstract]
Transactions with Affiliates	TRANSACTIONS WITH AFFILIATES We are a participant in WPZ’s cash management program. At June 30, 2018, the advances due from us to WPZ totaled approximately $90.1 million and at December 31, 2017, the advances due to us by WPZ totaled approximately $137.7 million. These advances are represented by demand notes and are classified as Payables - Advances from affiliate and Receivables - Advances to affiliate in the accompanying Balance Sheet. The interest rate on these intercompany demand notes is based upon the daily overnight investment rate paid on WPZ’s excess cash at the end of each month, which was 1.80 percent at June 30, 2018. The interest income/expense from these advances was minimal during the three and six months ended June 30, 2018 and June 30, 2017. Such interest income/expense is included in Other (Income) and Other Expenses – Miscellaneous other (income) expenses, net on the accompanying Statement of Comprehensive Income. We have no employees. Services necessary to operate our business are provided to us by Williams and certain affiliates of Williams. We reimburse Williams and its affiliates for all direct and indirect expenses incurred or payments made (including salary, bonus, incentive compensation, and benefits) in connection with these services. Employees of Williams also provide general administrative and management services to us, and we are charged for certain administrative expenses incurred by Williams. These charges are either directly identifiable or allocated to our assets. Direct charges are for goods and services provided by Williams at our request. Allocated charges are based on a three-factor formula, which considers revenues; property, plant, and equipment; and payroll. In management’s estimation, the allocation methodologies used are reasonable and result in a reasonable allocation to us of our costs of doing business incurred by Williams. We were billed $23.6 million and $45.7 million in the three and six months ended June 30, 2018, respectively, and $23.2 million and $46.2 millions in the three and six months ended June 30, 2017, respectively, for these services. Such expenses are primarily included in General and administrative and Operation and maintenance expenses on the accompanying Statement of Comprehensive Income. During the six months ended June 30, 2018 and 2017, we declared and paid cash distributions to our parent of $87.0 million and $107.0 million, respectively. We have entered into various other transactions with certain related parties, the amounts of which were not significant. These transactions and the above-described transactions are made on the basis of commercial relationships and prevailing market prices or general industry practices.

TRANSACTIONS WITH AFFILIATES

We are a participant in WPZ’s cash management program. At June 30, 2018, the advances due from us to WPZ totaled approximately $90.1 million and at December 31, 2017, the advances due to us by WPZ totaled approximately $137.7 million. These advances are represented by demand notes and are classified as Payables - Advances from affiliate and Receivables - Advances to affiliate in the accompanying Balance Sheet. The interest rate on these intercompany demand notes is based upon the daily overnight investment rate paid on WPZ’s excess cash at the end of each month, which was 1.80 percent at June 30, 2018. The interest income/expense from these advances was minimal during the three and six months ended June 30, 2018 and June 30, 2017. Such interest income/expense is included in Other (Income) and Other Expenses – Miscellaneous other (income) expenses, net on the accompanying Statement of Comprehensive Income.

We have no employees. Services necessary to operate our business are provided to us by Williams and certain affiliates of Williams. We reimburse Williams and its affiliates for all direct and indirect expenses incurred or payments made (including salary, bonus, incentive compensation, and benefits) in connection with these services. Employees of Williams also provide general administrative and management services to us, and we are charged for certain administrative expenses incurred by Williams. These charges are either directly identifiable or allocated to our assets. Direct charges are for goods and services provided by Williams at our request. Allocated charges are based on a three-factor formula, which considers revenues; property, plant, and equipment; and payroll. In management’s estimation, the allocation methodologies used are reasonable and result in a reasonable allocation to us of our costs of doing business incurred by Williams. We were billed $23.6 million and $45.7 million in the three and six months ended June 30, 2018, respectively, and $23.2 million and $46.2 millions in the three and six months ended June 30, 2017, respectively, for these services. Such expenses are primarily included in General and administrative and Operation and maintenance expenses on the accompanying Statement of Comprehensive Income.

During the six months ended June 30, 2018 and 2017, we declared and paid cash distributions to our parent of $87.0 million and $107.0 million, respectively.

We have entered into various other transactions with certain related parties, the amounts of which were not significant. These transactions and the above-described transactions are made on the basis of commercial relationships and prevailing market prices or general industry practices.