Debt and Financing Arrangements (Details Textual) (USD $)	Sep. 30, 2012
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 400,000,000
$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 | Letter Of Credit Capacity [Member] | Williams Partners L.P. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,300,000,000
Letters of Credit Outstanding, Amount	$ 0