Financial Instruments, Derivatives, Guarantees and Concentration of Credit Risk (Details 1)	Jun. 30, 2011 MMBtu
Exploration & Production | Options | Risk Management
Derivative Instruments Designated as Hedging Instruments
Net notional quantity of derivative designated As hedging instrument	(50,600,000)
Exploration & Production | Index | Risk Management
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	(46,487,263)
Midstream Canada & Olefins | Index | Risk Management
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	(144,300)
Williams Partners | Basis | Risk Management
Derivative Instruments Designated as Hedging Instruments
Net notional quantity of derivative designated As hedging instrument	9,355,000
Exploration & Production | Basis | Other Risk Management
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	(8,007,500)
Exploration & Production | Basis | Risk Management
Derivative Instruments Designated as Hedging Instruments
Net notional quantity of derivative designated As hedging instrument	(258,680,000)
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	(15,965,000)
Williams Partners | Central Hub Risk | Risk Management
Derivative Instruments Designated as Hedging Instruments
Net notional quantity of derivative designated As hedging instrument	(2,960,000)
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	(54,000)
Exploration & Production | Central Hub Risk | Risk Management
Derivative Instruments Designated as Hedging Instruments
Net notional quantity of derivative designated As hedging instrument	(258,680,000)
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	(12,940,000)
Midstream Canada & Olefins | Central Hub Risk | Risk Management
Derivative Instruments Not Designated as Hedging Instruments
Net notional quantity of price risk derivative instruments not designated as hedging instruments	50,000