Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Operating Activities:
Net Income	$ 13.6us-gaap_NetIncomeLoss	$ 12.6us-gaap_NetIncomeLoss
Adjustments to Reconcile Net Income to Cash Provided by Operating Activities:
Depreciation and Amortization	11.4	10.2
Deferred Tax Provision	8.8us-gaap_DeferredIncomeTaxExpenseBenefit	7.0us-gaap_DeferredIncomeTaxExpenseBenefit
Changes in Working Capital Items:
Accounts Receivable	(25.2)	(17.3)
Accrued Revenue	6.3	7.0
Exchange Gas Receivable	11.0	9.5
Regulatory Liabilities	8.7	3.4
Accounts Payable	(9.4)	(6.3)
Other Changes in Working Capital Items	1.0	3.1
Deferred Regulatory and Other Charges	(0.5)	(1.9)
Other, net	2.1	1.4
Cash Provided by Operating Activities	27.8	28.7
Investing Activities:
Property, Plant and Equipment Additions	(13.1)	(9.2)
Cash (Used in) Investing Activities	(13.1)	(9.2)
Financing Activities:
Proceeds from (Repayment of) Short-Term Debt, net	2.7	(1.0)
Repayment of Long-Term Debt	(0.2)us-gaap_RepaymentsOfLongTermDebt	(0.1)us-gaap_RepaymentsOfLongTermDebt
Increase / (Decrease) in Capital Lease Obligations	0.7	(0.1)
Net Decrease in Exchange Gas Financing	(10.5)	(8.8)
Dividends Paid	(4.9)us-gaap_PaymentsOfDividends	(4.8)us-gaap_PaymentsOfDividends
Proceeds from Issuance of Common Stock	0.3	0.3
Other, net		(0.1)
Cash (Used in) Financing Activities	(11.9)	(14.6)
Net Increase in Cash and Cash Equivalents	2.8	4.9
Cash and Cash Equivalents at Beginning of Period	8.4	9.4
Cash and Cash Equivalents at End of Period	11.2	14.3
Supplemental Cash Flow Information:
Interest Paid	3.1us-gaap_InterestPaidNet	3.0us-gaap_InterestPaidNet
Income Taxes Paid	1.4us-gaap_IncomeTaxesPaidNet	0.3us-gaap_IncomeTaxesPaidNet
Non-cash Investing Activity:
Capital Expenditures Included in Accounts Payable	$ 0.4	$ 0.4

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