CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Current Assets:
Cash and cash equivalents	$ 10.9	$ 21.9	$ 84.2	$ 55.0
Receivables:
Trade, net	79.0	98.6
Affiliates	0.5	0
Other	10.6	22.5
Gas transportation receivables	6.7	5.8
Costs recoverable from customers	4.2	9.8
Gas stored underground	6.1	1.7
Prepayments	19.5	13.9
Other current assets	2.1	1.8
Total current assets	139.6	176.0
Property, Plant and Equipment:
Natural gas transmission and other plant	7,603.7	7,536.0
Construction work in progress	158.3	110.6
Property, plant and equipment, gross	7,762.0	7,646.6
Less-accumulated depreciation and amortization	1,167.7	999.2
Property, plant and equipment, net	6,594.3	6,647.4
Other Assets:
Goodwill	215.3	215.3
Gas stored underground	109.8	107.9
Costs recoverable from customers	15.0	15.3
Other	99.8	104.5
Total other assets	439.9	443.0
Total Assets	7,173.8	7,266.4
Payables:
Trade	34.5	44.7
Affiliates	4.7	3.2
Other	13.7	7.3
Gas Payables:
Transportation	7.7	5.0
Storage	1.1	0.1
Accrued taxes, other	63.7	44.2
Accrued interest	29.4	45.2
Accrued payroll and employee benefits	22.5	18.4
Deferred income	20.9	9.4
Other current liabilities	15.3	25.2
Total current liabilities	213.5	202.7
Long-term debt	3,063.7	3,298.7
Long-term debt - affiliate	100.0	100.0
Total long-term debt	3,163.7	3,398.7
Other Liabilities and Deferred Credits:
Pension liability	20.7	27.3
Asset retirement obligation	22.3	19.2
Provision for other asset retirement	57.7	54.5
Payable to affiliate	16.0	16.0
Other	54.9	61.0
Total other liabilities and deferred credits	171.6	178.0
Commitments and Contingencies
Partners' Capital:
Common units - 196.5 million and 175.7 million units issued and outstanding as of September 30, 2012 and December 31, 2011	2,936.7	2,514.1
Class B units - 22.9 million units issued and outstanding as of September 30, 2012 and December 31, 2011	678.4	678.7
General partner	70.7	62.0
Predecessor equity	0	281.6
Accumulated other comprehensive loss	(60.8)	(49.4)
Total partners' capital	3,625.0	3,487.0
Total Liabilities and Partners' Capital	$ 7,173.8	$ 7,266.4