Consolidated Statement of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Activities
Net Income	$ 125.5	$ 104.7	$ 97.1
Allowance for Funds Used During Construction - Equity	(7.8)	(4.6)	(5.1)
Income from Equity Investments, Net of Dividends	(2.6)	(4.2)	(3.7)
Loss (Gain) on Sale of Assets / Investments	(0.2)	(2.6)	0.2
Depreciation Expense	135.7	116.6	100.2
Other Amortization	0.7	1.0	1.0
Amortization of Power Purchase Agreements	(12.7)	0	0
Deferred Income Tax Expense	32.7	28.6	37.5
Share-Based Compensation Expense	2.3	2.4	2.1
ESOP Compensation Expense	9.1	8.4	7.7
Defined Benefit Pension and Other Postretirement Benefit Expense	12.8	21.0	27.5
Bad Debt Expense	1.8	1.3	1.0
Changes in Operating Assets and Liabilities
Accounts Receivable	(3.5)	(8.6)	(10.1)
Inventories	(17.5)	10.5	(0.7)
Prepayments and Other	4.8	(1.4)	(6.5)
Accounts Payable	10.9	1.1	(1.5)
Other Current Liabilities	(3.5)	1.4	21.8
Cash Contributions to Defined Benefit Pension and Other Postretirement Plans	0	(10.8)	(8.8)
Changes in Regulatory and Other Non-Current Assets	(21.3)	(18.3)	(20.9)
Changes in Regulatory and Other Non-Current Liabilities	2.6	(7.1)	0.8
Cash from Operating Activities	269.8	239.4	239.6
Investing Activities
Proceeds from Sale of Available-for-sale Securities	3.6	16.1	1.5
Payments for Purchase of Available-for-sale Securities	(5.0)	(4.7)	(1.8)
Acquisitions of Subsidiaries – Net of Cash Acquired	(60.3)	0	0
Investment in ATC	(3.9)	(3.1)	(4.7)
Changes to Other Investments	33.0	(12.3)	(9.6)
Additions to Property, Plant and Equipment	(572.8)	(328.5)	(405.8)
Construction Costs for Development Project	(25.7)	0	0
Changes in Escrow for Acquisition	5.4	(5.4)	0
Proceeds from Sale of Assets	0	1.3	0.3
Cash for Investing Activities	(625.7)	(336.6)	(420.1)
Financing Activities
Proceeds from Issuance of Common Stock	200.6	98.2	77.0
Proceeds from Issuance of Long-Term Debt	375.0	169.8	180.6
Changes in Restricted Cash	(1.8)	0	0
Changes in Notes Payable	3.7	0	(1.1)
Reductions of Long-Term Debt	(134.5)	(77.7)	(25.9)
Acquisition of Non-Controlling Interest	(6.0)	0	0
Construction Deposits Received for Development Project	54.3	0	0
Debt Issuance Costs	(3.1)	(1.4)	(1.3)
Dividends on Common Stock	(83.8)	(75.2)	(69.1)
Cash from Financing Activities	404.4	113.7	160.2
Change in Cash and Cash Equivalents	48.5	16.5	(20.3)
Cash and Cash Equivalents at Beginning of Period	97.3	80.8	101.1
Cash and Cash Equivalents at End of Period	$ 145.8	$ 97.3	$ 80.8