Debt, Financing Arrangements and Leases (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 400,000,000
Maximum ratio of debt to capitalization	65.00%
LineOfCreditFacilityCommitmentFeePercentage	0.20%
Leases [Abstract]
Office space initial lease term	10 years
Minimum office space lease renewal option	5 years
Maximum office space lease renewal option	10 years
Operating Expenses [Abstract]
LeaseAndRentalExpense	2,200,000	2,400,000	2,200,000
Williams Partners L.P. [Member]
Line of Credit Facility [Line Items]
Maximum ratio of debt to EBITDA	5.0
Maximum ratio of debt to EBITDA after acquisitions	5.5
Aggregate purchase price of acquistions increasing debt to EBITDA ratio	50,000,000
$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
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding	0
$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	375,000,000
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