Consolidated Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities
Net Income	$ 141.5	$ 125.5	$ 104.7
Allowance for Funds Used During Construction – Equity	(3.3)	(7.8)	(4.6)
Income from Equity Investments – Net of Dividends	(1.8)	(2.6)	(4.2)
Impairment of Real Estate	36.3	0.0	0.0
Gain on Sales of Investments and Property, Plant and Equipment	(0.2)	(0.2)	(2.6)
Depreciation Expense	165.9	135.7	116.6
Amortization of Power Purchase Agreements	(23.2)	(12.7)	0.0
Amortization of Other Intangible Assets and Other Assets	5.6	0.7	1.0
Deferred Income Tax Expense	25.1	32.7	28.6
Share-Based Compensation Expense	2.6	2.3	2.4
ESOP Compensation Expense	9.0	9.1	8.4
Defined Benefit Pension and Other Postretirement Benefit Expense	15.4	12.8	21.0
Bad Debt Expense	1.6	1.8	1.3
Changes in Operating Assets and Liabilities
Accounts Receivable	1.1	(3.5)	(8.6)
Inventories	(22.1)	(17.5)	10.5
Prepayments and Other	3.7	4.8	(1.4)
Accounts Payable	(19.3)	10.9	1.1
Other Current Liabilities	5.1	(3.5)	1.4
Cash Contributions to Defined Benefit Pension and Other Postretirement Plans	0.0	0.0	(10.8)
Changes in Regulatory and Other Non-Current Assets	0.6	(21.3)	(18.3)
Changes in Regulatory and Other Non-Current Liabilities	(3.5)	2.6	(7.1)
Cash from Operating Activities	340.1	269.8	239.4
Investing Activities
Proceeds from Sale of Available-for-sale Securities	1.7	3.6	16.1
Payments for Purchase of Available-for-sale Securities	(2.3)	(5.0)	(4.7)
Acquisitions of Subsidiaries – Net of Cash Acquired	(333.3)	(60.3)	0.0
Investment in ATC	(1.6)	(3.9)	(3.1)
Changes to Other Investments	3.1	33.0	(12.3)
Additions to Property, Plant and Equipment	(286.8)	(572.8)	(328.5)
Construction Costs for Development Project	0.0	(25.7)	0.0
Cash in Escrow for Acquisition	0.0	5.4	(5.4)
Proceeds from Sale of Property, Plant and Equipment	0.4	0.0	1.3
Cash for Investing Activities	(618.8)	(625.7)	(336.6)
Financing Activities
Proceeds from Issuance of Common Stock	161.2	200.6	98.2
Proceeds from Issuance of Long-Term Debt	324.5	375.0	169.8
Changes in Restricted Cash	8.5	(1.8)	0.0
Changes in Notes Payable	(2.1)	3.7	0.0
Reductions of Long-Term Debt	(160.2)	(134.5)	(77.7)
Acquisition of Non-Controlling Interest	0.0	(6.0)	0.0
Construction Deposits Received for Development Project	0.0	54.3	0.0
Debt Issuance Costs	(4.1)	(3.1)	(1.4)
Dividends on Common Stock	(97.9)	(83.8)	(75.2)
Cash from Financing Activities	229.9	404.4	113.7
Change in Cash and Cash Equivalents	(48.8)	48.5	16.5
Cash and Cash Equivalents at Beginning of Period	145.8	97.3	80.8
Cash and Cash Equivalents at End of Period	$ 97.0	$ 145.8	$ 97.3