Contingent Liabilities (Details Textual) $ in Millions	Sep. 30, 2015 USD ($)
Loss Contingencies [Line Items]
Accrued Environmental Loss liabilities	$ 41
Former Alaska Refinery [Member]
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Maximum	32
Environmental Protection Agency [Member]
Loss Contingencies [Line Items]
Accrued Environmental Loss liabilities	8
Natural gas underground storage facilities [Member]
Loss Contingencies [Line Items]
Accrued Environmental Loss liabilities	7
Former Operations [Member]
Loss Contingencies [Line Items]
Accrued Environmental Loss liabilities	26
Williams Partners [Member] | General Liability [Member] | Geismar Incident [Member]
Loss Contingencies [Line Items]
Aggregate Annual Limit of Insurance	610
Insurance deductibles	$ 2