Debt and Financing Arrangements Line of Credit Facility (Details) $ in Millions	Mar. 31, 2019 USD ($)
Letter of credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 500.0
Williams Companies Inc [Member]
Line of Credit Facility [Line Items]
Commercial paper, outstanding	1,000.0
Williams Companies Inc [Member] | Letter of credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,000.0
Credit Agreement Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	500.0
Letters of credit outstanding, amount	0.0
Line of credit facility, amount outstanding	0.0
Credit Agreement Member] | Williams Companies Inc [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	4,500.0
Additional Amount By Which Credit Facility Can Be Increased	500.0
Commercial Paper [Member] | Williams Companies Inc [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 4,000.0