Contingent Liabilities and Commitments (Details) $ in Millions	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Accrued Environmental Loss liabilities	$ 40
Capital Addition Purchase Commitments [Member]
Loss Contingencies [Line Items]
Commitments for construction and acquisition of property, plant and equipment	770
Former Alaska Refinery [Member]
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Maximum	32
Gas Pipeline [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	25
Williams Partners [Member] | General Liability [Member] | Geismar Incident [Member]
Loss Contingencies [Line Items]
Aggregate Annual Limit of Insurance	610
Insurance Deductibles	$ 2