CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating Activities:
Net income	$ 108.1	$ 97.2
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	85.8	82.9
Amortization of deferred costs and other	2.3	2.7
Gain on sale of assets and impairments	0.0	(0.4)
Changes in operating assets and liabilities:
Trade and other receivables	19.8	4.8
Gas receivables and storage assets	(2.9)	4.3
Costs recoverable from customers	7.4	(6.1)
Other assets	3.8	1.6
Trade and other payables	(14.4)	(4.6)
Gas payables	(2.7)	(0.8)
Accrued liabilities	(40.0)	(31.2)
Other liabilities	(0.8)	1.5
Net cash provided by operating activities	166.4	151.9
Investing Activities:
Capital expenditures	(74.0)	(110.9)
Proceeds from sale of operating assets	0.1	0.5
Net cash used in investing activities	(73.9)	(110.4)
Financing Activities:
Proceeds from borrowings on revolving credit agreement	125.0	145.0
Repayment of borrowings on revolving credit agreement	(180.0)	(145.0)
Principal payment of finance lease obligation	(0.2)	(0.1)
Distributions paid	(25.6)	(25.6)
Net cash used in financing activities	(80.8)	(25.7)
Increase in cash and cash equivalents	11.7	15.8
Cash and cash equivalents at beginning of period	3.6	17.6
Cash and cash equivalents at end of period	$ 15.3	$ 33.4