CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating Activities:
Net income	$ 212.8	$ 214.0
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	241.4	238.7
Amortization of deferred costs and other	4.9	4.3
(Gain) loss on sale of assets and impairments	47.1	(0.1)
Changes in operating assets and liabilities:
Trade and other receivables	31.2	10.0
Gas receivables and storage assets	(1.3)	0.0
Costs recoverable from customers	3.0	0.0
Other assets	(4.4)	(7.1)
Trade and other payables	(22.0)	(27.0)
Other payables, affiliates	0.0	(0.1)
Gas payables	(5.4)	2.9
Accrued liabilities	9.5	28.7
Other liabilities	(13.6)	(10.1)
Net cash provided by operating activities	503.2	454.2
Investing Activities:
Capital expenditures	(496.0)	(432.4)
Proceeds from sale of operating assets	63.7	0.2
Net cash used in investing activities	(432.3)	(432.2)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	494.0	539.1
Repayment of borrowings from long-term debt	(575.0)	0.0
Proceeds from borrowings on revolving credit agreement	505.0	255.0
Repayment of borrowings on revolving credit agreement, including financing fees	(400.0)	(630.8)
Principal payment of capital lease obligation	(0.3)	(0.3)
Advances from affiliates	0.1	0.0
Distributions paid	(76.7)	(76.7)
Net cash (used in) provided by financing activities	(52.9)	86.3
Increase in cash and cash equivalents	18.0	108.3
Cash and cash equivalents at beginning of period	4.6	3.1
Cash and cash equivalents at end of period	$ 22.6	$ 111.4