CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Activities:
Net Income	$ 101.0	$ 77.7
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	79.0	81.6
Amortization of deferred costs	1.3	1.7
Asset impairment	0.0	0.1
Changes in operating assets and liabilities:
Trade and other receivables	6.2	(0.2)
Gas receivables and storage assets	0.2	(0.4)
Costs recoverable from customers	0.0	1.0
Other assets	0.2	2.9
Trade and other payables	(30.3)	13.1
Other payables, affiliates	0.4	(0.7)
Gas payables	(1.6)	0.3
Accrued liabilities	(35.1)	(34.5)
Other liabilities	1.0	4.2
Net cash provided by operating activities	122.3	146.8
Investing Activities:
Capital expenditures	(105.6)	(62.2)
Proceeds from sale of operating assets	0.1	0.0
Net cash used in investing activities	(105.5)	(62.2)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	0.0	247.1
Repayment of borrowings from long-term debt and term loan	0.0	(300.0)
Proceeds from borrowings on revolving credit agreement	175.0	340.0
Repayment of borrowings on revolving credit agreement	(160.0)	(410.0)
Principal payment of capital lease obligation	(0.1)	(0.1)
Distributions paid	(25.5)	(24.8)
Proceeds from sale of common units	0.0	83.2
Capital contributions from general partner	0.0	2.2
Net cash used in financing activities	(10.6)	(62.4)
Increase in cash and cash equivalents	6.2	22.2
Cash and cash equivalents at beginning of period	3.1	6.6
Cash and cash equivalents at end of period	$ 9.3	$ 28.8