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Property, Plant, and Equipment (Details ARO) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Asset Retirement Obligations    
Asset Retirement Obligations, Noncurrent $ 791us-gaap_AssetRetirementObligationsNoncurrent $ 497us-gaap_AssetRetirementObligationsNoncurrent
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning balance 561us-gaap_AssetRetirementObligation 579us-gaap_AssetRetirementObligation
Liabilities incurred 101us-gaap_AssetRetirementObligationLiabilitiesIncurred 8us-gaap_AssetRetirementObligationLiabilitiesIncurred
Liabilities settled (21)us-gaap_AssetRetirementObligationLiabilitiesSettled [1] (31)us-gaap_AssetRetirementObligationLiabilitiesSettled [1]
Accretion expense 44us-gaap_AssetRetirementObligationAccretionExpense 53us-gaap_AssetRetirementObligationAccretionExpense
Revisions 146us-gaap_AssetRetirementObligationRevisionOfEstimate [2] (48)us-gaap_AssetRetirementObligationRevisionOfEstimate [2]
Ending balance 831us-gaap_AssetRetirementObligation 561us-gaap_AssetRetirementObligation
Charges related to leak at underground storage facility [Member]    
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Liabilities settled (7)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ us-gaap_UnusualOrInfrequentItemAxis
= wmb_ChargesRelatedToLeakAtUndergroundNaturalGasStorageFacilityMember		 (25)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ us-gaap_UnusualOrInfrequentItemAxis
= wmb_ChargesRelatedToLeakAtUndergroundNaturalGasStorageFacilityMember
Revisions   9us-gaap_AssetRetirementObligationRevisionOfEstimate
/ us-gaap_UnusualOrInfrequentItemAxis
= wmb_ChargesRelatedToLeakAtUndergroundNaturalGasStorageFacilityMember
Asset Retirement Obligation Costs [Member]    
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Transco's annual funding commitment for ARO $ 36us-gaap_OtherCommitmentDueInNextTwelveMonths
/ us-gaap_UnusualOrInfrequentItemAxis
= us-gaap_AssetRetirementObligationCostsMember		  
[1] For 2014 and 2013 liabilities settled include $7 million and $25 million, respectively, related to the abandonment of certain of Transco’s natural gas storage caverns that are associated with a leak in 2010.
[2] Several factors are considered in the annual review process, including inflation rates, current estimates for removal cost, discount rates, and the estimated remaining life of the assets. The 2014 revisions primarily reflect an increase in the estimated retirement costs for our offshore pipelines, an increase in the inflation rate and decreases in the discount rates used in the annual review process. The 2013 revision primarily reflects increases in the estimated remaining useful life of the assets. The 2013 revision also includes an increase of $9 million related to changes in the timing and method of abandonment on certain of Transco’s natural gas storage caverns that were associated with a leak in 2010.