CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Operating Activities:
Net Income	$ 171.8	$ 157.7
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	134.1	124.4
Amortization of deferred costs	2.7	2.4
Asset impairment	1.2	7.1
Net gain on sale of operating assets	(16.2)	(3.6)
Changes in operating assets and liabilities:
Trade and other receivables	(0.5)	22.4
Other receivables, affiliates	0.1	0
Gas receivables and storage assets	18.2	(5.5)
Costs recoverable from customers	0.6	3.8
Other assets	11.8	(10.1)
Trade and other payables	(27.9)	0.1
Other payables, affiliates	0.7	(3.1)
Gas payables	0.1	2.7
Accrued liabilities	1.5	(0.6)
Other liabilities	(12.8)	(13.4)
Net cash provided by operating activities	285.2	284.3
Investing Activities:
Capital expenditures	(132.2)	(90.9)
Proceeds from sale of operating assets	21.2	2.4
Proceeds from insurance and other recoveries	1.4	5.4
Investment in unconsolidated affiliates	(21.4)	0
Net cash used in investing activities	(131.0)	(83.1)
Financing Activities:
Proceeds from long-term debt, net of issuance costs	0	296.5
Proceeds from borrowings on revolving credit agreement	458.0	1,000.0
Repayment of borrowings on revolving credit agreement	(740.0)	(1,243.5)
Payments of financing fees related to revolving credit facility	0	(3.8)
Advances from affiliate	(2.4)	2.6
Repayment of contribution received related to predecessor equity	0	(284.8)
Distributions paid	(256.4)	(228.9)
Capital contributions from noncontrolling interests	16.1	0
Proceeds from sale of common units	368.7	245.0
Capital contribution from general partner	7.8	5.2
Net cash used in financing activities	(148.2)	(211.7)
Increase (decrease) in cash and cash equivalents	6.0	(10.5)
Cash and cash equivalents at beginning of period	3.9	21.9
Cash and cash equivalents at end of period	$ 9.9	$ 11.4