Debt Leases and Banking Arrangements (Details 1) (USD $) In Millions, unless otherwise specified				6 Months Ended
	Jul. 31, 2013	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Williams Partners L. P. [Member]	Jul. 31, 2013 Williams Partners L. P. [Member]	Jul. 31, 2013 Transcontinental Gas Pipe Line Company, LLC [Member]	Jul. 31, 2013 Northwest Pipeline LLC [Member]	Jun. 30, 2013 Commercial Paper [Member] Williams Partners L. P. [Member]	Jun. 30, 2013 Letter of Credit [Member]	Jun. 30, 2013 Letter of Credit [Member] Williams Partners L. P. [Member]	Jun. 30, 2013 Bilateral bank agreements for letters of credit [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	$ 1,500	$ 900		$ 2,400	$ 2,500	$ 500	$ 500	$ 2,000	$ 700	$ 1,300
Credit facility, loans outstanding		0		0
Credit facility, letters of credit outstanding		0		0							16
Commercial paper, outstanding		710	0	710
Commercial paper, maximum maturity				397 days
Commercial paper, weighted average interest rate				0.42%
Additional amount by which credit facility can be increased	$ 500				$ 500