Contingent Liabilities (Details) - USD ($)	Sep. 26, 2016	Jun. 16, 2016	May 20, 2016	Sep. 30, 2016
Loss Contingencies [Line Items]
Litigation Judgment or Settlement, Amount		$ 170,000
Accrued Environmental Loss liabilities				$ 37,000,000
Energy Transfer Merger [Member]
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value			$ 1,480,000,000
Gas Pipeline [Member]
Loss Contingencies [Line Items]
Accrued Environmental Loss liabilities				7,000,000
Natural gas underground storage facilities [Member]
Loss Contingencies [Line Items]
Accrued Environmental Loss liabilities				7,000,000
Former Operations [Member]
Loss Contingencies [Line Items]
Accrued Environmental Loss liabilities				23,000,000
Williams Partners [Member] | Geismar Incident [Member]
Loss Contingencies [Line Items]
Litigation Judgment or Settlement, Amount	$ 13,600,000
Williams Partners [Member] | General Liability [Member] | Geismar Incident [Member]
Loss Contingencies [Line Items]
Aggregate Limit of Insurance				610,000,000
Insurance deductibles				2,000,000
Maximum [Member] | Former Alaska Refinery [Member]
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Maximum				$ 32,000,000