Financial Instruments, Derivatives, Guarantees and Concentration of Credit Risk (Details 1) (Risk Management)	Dec. 31, 2011 bbl
Basis Risk | Williams Partners [Member]
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	240,000
Central Hub Risk | Williams Partners [Member]
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	45,000
Central Hub Risk | Midstream Canada & Olefins [Member]
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	(25,000)