Acquisitions (Details) (USD $)	12 Months Ended							2 Months Ended				4 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 20, 2012 Access Midstream Partners [Member]	Dec. 31, 2012 Access Midstream Partners [Member]	Dec. 20, 2012 Access Midstream Ventures, L.L.C. [Member] General Partner [Member]	Dec. 20, 2012 Access Midstream Partners L.P. (ACMP) [Member] Limited Partner [Member]	Feb. 17, 2012 Laser [Member] Williams Partners [Member] in mi	Feb. 17, 2012 Laser [Member] Williams Partners [Member] Customer Contracts [Member]	Feb. 17, 2012 Laser [Member] Williams Partners [Member] Customer Relationships [Member]	Feb. 17, 2012 Laser [Member] Williams Partners [Member] Other Intangible Assets [Member]	Apr. 27, 2012 Caiman [Member] Williams Partners [Member]	Dec. 31, 2012 Caiman [Member] Williams Partners [Member]	Apr. 27, 2012 Caiman [Member] Williams Partners [Member] Customer Contracts [Member]	Apr. 27, 2012 Caiman [Member] Williams Partners [Member] Customer Relationships [Member]	Apr. 27, 2012 Caiman [Member] Williams Partners [Member] Other Intangible Assets [Member]
Business Acquisition, Entity Acquired and Reason for Acquisition [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired								100.00%				100.00%
Business Acquisition, Cost of Acquired Entity, Purchase Price [Abstract]
Business Acquisition, Cost of Acquired Entity, Cash Paid								$ 325,000,000				$ 1,720,000,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares								7,531,381				11,779,296
Business Acquisition, Cost of Acquired Entity, Equity Interests Issued and Issuable								441,000,000				603,000,000
Number Of Miles Of Pipeline Acquired In Pennsylvania								33
Diameter In Inches Of Pipeline Acquired In Pennsylvania								16
Number Of Miles Of Pipeline Acquired In New York								10
Business Combination, Acquisition Related Costs													16,000,000
Business Acquisition, Purchase Price Allocation [Abstract]
Assets held-for-sale								18,000,000				0
Other current assets								3,000,000				16,000,000
Property, plant and equipment								158,000,000				656,000,000
Intangible assets									316,000,000	0	2,000,000			1,141,000,000	250,000,000	2,000,000
Current liabilities								(21,000,000)				(94,000,000)
Noncurrent liabilities								0				(3,000,000)
Identifiable net assets acquired								476,000,000				1,968,000,000
Goodwill								290,000,000				359,000,000
Total								766,000,000				2,327,000,000
Business Acquisition, Purchase Price Allocation, Goodwill [Abstract]
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount								290,000,000				359,000,000
Intangible Assets Disclosure [Abstract]
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life (years)				18 years				30 years				30 years
Percentage of Finite Lived Intangible Assets Impacted By Our Intent Or Ability To Renew Or Extend Arrangement								70.00%				36.00%
Acquired Finite-lived Intangible Asset, Weighted-Average Period before Renewal or Extension								9 years				18 years
Amortization of Intangible Assets	43,000,000	2,000,000	0
Finite-Lived Intangible Assets, Accumulated Amortization	45,000,000	2,000,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	58,000,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two	58,000,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	58,000,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	58,000,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	58,000,000
Equity Method Investments [Abstract]
Equity Method Investment, Aggregate Cost				2,190,000,000
Equity Method Investment, Ownership Percentage				25.00%	25.00%	50.00%	24.00%
Master limited partnership, general partner ownership percentage				2.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 59,000,000			$ 1,270,000,000