CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities:
Net income	$ 177.3	$ 212.8
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	256.6	241.4
Amortization of deferred costs and other	8.8	4.9
(Gain) loss on sale of assets and impairments	(0.7)	47.1
Changes in operating assets and liabilities:
Trade and other receivables	10.9	31.2
Gas receivables and storage assets	0.6	(1.3)
Costs recoverable from customers	(11.1)	3.0
Other assets	(7.9)	(4.4)
Trade and other payables	2.6	(22.0)
Gas payables	1.2	(5.4)
Accrued liabilities	16.0	9.5
Other liabilities	1.0	(13.6)
Net cash provided by operating activities	455.3	503.2
Investing Activities:
Capital expenditures	(354.8)	(496.0)
Proceeds from sale of operating assets	0.9	63.7
Net cash used in investing activities	(353.9)	(432.3)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	0.0	494.0
Repayment of borrowings from long-term debt	(185.0)	(575.0)
Proceeds from borrowings on revolving credit agreement	525.0	505.0
Repayment of borrowings on revolving credit agreement	(355.0)	(400.0)
Principal payment of capital lease obligation	(0.4)	(0.3)
Advances from affiliates	0.1	0.1
Distributions paid	(76.7)	(76.7)
Net cash used in financing activities	(92.0)	(52.9)
Increase in cash and cash equivalents	9.4	18.0
Cash and cash equivalents at beginning of period	17.6	4.6
Cash and cash equivalents at end of period	$ 27.0	$ 22.6