Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended								12 Months Ended			12 Months Ended		1 Months Ended			3 Months Ended	4 Months Ended	12 Months Ended
	Nov. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Correction Increasing Operating And Maintenance Expenses And Decreasing Selling General And Administrative Expenses	Dec. 31, 2010 Correction Increasing Operating And Maintenance Expenses And Decreasing Selling General And Administrative Expenses	Dec. 31, 2012 Gulfstar One	Dec. 31, 2011 Gulfstar One	Dec. 31, 2012 Gulfstar One Maximum [Member]	Dec. 31, 2012 Constitution Pipeline Company LLC	Dec. 31, 2012 Gulfstar One To Be Sold To Third Party	Dec. 31, 2012 Gulfstar One Partner	Dec. 31, 2012 Transcontinental Gas Pipe Line Company, LLC	Dec. 31, 2012 Northwest Pipeline GP	Nov. 30, 2012 Williams Partners L.P.	Aug. 31, 2012 Williams Partners L.P.	Apr. 30, 2012 Williams Partners L.P.	Mar. 31, 2012 Williams Partners L.P.	Apr. 27, 2012 Williams Partners L.P.	Dec. 31, 2012 Williams Partners L.P.	Dec. 31, 2012 Gulfstream Natural Gas System, L.L.C.
Description of Business, Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Voting interest in unconsolidated companies, minimum		20.00%
Voting interest in unconsolidated companies, maximum		50.00%
Former business, ownership percentage			100.00%
Spinoff Shares Conversion Ratio			0.33
Minimum period of construction for capitalization of interest		3 months
Minimum total project cost for capitalization of interest		$ 1
Goodwill		649	0
Other intangibles		1,704	44
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage																					50.00%
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Subsidiary, ownership percentage													100.00%	100.00%
Sale Of Stock Number Of Shares Issued In Transaction																9,775,000	10,973,368	8,050,000	16,360,133
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares																		7,531,381	11,779,296
Master limited partnership, general partner ownership percentage															2.00%
Master limited partnership, ownership percentage																				70.00%
Variable Interest Entities:
Carrying value of construction work in process							532	103		24
Carrying value of deferred revenue							109	101
Estimated remaining construction costs									475	680
Carrying value of cash and cash equivalents										8
Carrying value of accounts payable							124	33		4
Variable Interest Entity Ownership Percentage										51.00%	49.00%
Proportionate share of project costs contributed												225
Regulatory Assets		405	411
Regulatory Liabilities		265	206
Adjustments To Additional Paid In Capital Reallocation Of MinorityInterest		699
Noncontrolling Interest Increase From Stock Issuance And Business Combination		1,488
Increase To Deferred Tax Due To Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Changes Issuance Of Equity By Subsidiary To Noncontrolling Interests		416
Number of limited partner units received on contributing a business	42,778,812
Cash received on contributing a business	25
Percent Ownership Of Contributed Business	83.30%
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expenses		1,027	990	870	14	13
Selling, general, and administrative expenses		$ 571	$ 477	$ 504	$ (14)	$ (13)