Debt and Financing Arrangements (Details Textual) (USD $)	Sep. 30, 2012	Jul. 31, 2012
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 400,000,000
$375 Million, 5.4% Senior Notes due 2041 [Member]
Long-term Debt, by Current and Noncurrent [Abstract]
Debt Instrument, Face Amount	375,000,000
Debt Instrument, Interest Rate, Stated Percentage	5.40%
$400 Million, 4.45% Senior Notes due 2042 [Member]
Long-term Debt, by Current and Noncurrent [Abstract]
Debt Instrument, Face Amount	400,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.45%
Long-term Debt, Other Disclosures [Abstract]
Additional Interest Rate Accrued For Default Of Registration Rights Agreements First Period		0.25%
Additional Interest Rate Accrued For Default Of Registration Rights Agreements Each Subsequent Period		0.25%
MaximumAdditional Interest Rate Accrued For Default Of Registration Rights Agreements All Periods		0.50%
$325 Million, 8.875% Senior Notes due July 15, 2012 [Member]
Long-term Debt, by Current and Noncurrent [Abstract]
Debt Instrument, Face Amount	325,000,000
Debt Instrument, Interest Rate, Stated Percentage	8.875%
$2 billion unsecured credit facility superceeded September 2012 [Member] | Williams Partners L.P. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,000,000,000
Increased capacity of credit facility	400,000,000
$2.4 billion unsecured credit facility effective September 2012 | Williams Partners L.P. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,400,000,000
Line of Credit Facility, Amount Outstanding	0
Additional amount credit facility can be increased.	400,000,000
$2.4 billion unsecured credit facility effective September 2012 | Williams Partners L.P. [Member] | Letter of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,300,000,000
Letters of Credit Outstanding, Amount	$ 0