CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating Activities:
Net income	$ 156.4	$ 109.9
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	242.4	211.0
Amortization of deferred costs	6.3	4.3
Asset impairment	0.1	8.6
Net gain on sale of operating assets	(0.2)	(1.1)
Equity losses in unconsolidated affiliates	0.0	86.9
Changes in operating assets and liabilities:
Trade and other receivables	7.2	24.7
Other receivables, affiliates	0.0	0.9
Gas receivables and storage assets	(14.6)	(18.4)
Costs recoverable from customers	0.2	1.7
Other assets	(1.7)	(3.6)
Trade and other payables	8.1	0.6
Other payables, affiliates	(0.7)	(0.5)
Gas payables	(0.7)	(6.6)
Accrued liabilities	5.8	5.9
Other liabilities	21.6	(11.8)
Net cash provided by operating activities	430.2	412.5
Investing Activities:
Capital expenditures	(241.1)	(315.9)
Proceeds from sale of operating assets	0.3	2.9
Proceeds from other recoveries	6.2	6.3
Advances to affiliates	0.0	0.1
Investment in unconsolidated affiliates	0.0	(20.5)
Distributions from unconsolidated affiliates	0.0	10.7
Acquisition-related deposit	0.0	(29.5)
Net cash used in investing activities	(234.6)	(345.9)
Financing Activities:
Proceeds from long-term debt	247.1	0.0
Repayment of borrowings from long-term debt and term loan	(725.0)	(25.0)
Proceeds from borrowings on revolving credit agreement	980.0	340.0
Repayment of borrowings on revolving credit agreement, including financing fees	(738.6)	(330.0)
Principal payment of capital lease obligation	(0.3)	(0.3)
Advances from affiliate	0.6	0.1
Distributions paid	(76.0)	(74.4)
Proceeds from sale of common units	113.1	0.0
Capital contributions from general partner	2.3	0.0
Capital contributions from noncontrolling interests	0.0	8.2
Distributions paid to noncontrolling interests	0.0	(7.5)
Net cash used in financing activities	(196.8)	(88.9)
Decrease in cash and cash equivalents	(1.2)	(22.3)
Cash and cash equivalents at beginning of period	6.6	28.5
Cash and cash equivalents at end of period	$ 5.4	$ 6.2