Consolidated Balance Sheet - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Current Assets
Cash and Cash Equivalents		$ 27.5	$ 97.0
Accounts Receivable (Less Allowance of $3.1 and $1.0)		122.5	121.2
Inventories – Net		104.2	117.1
Prepayments and Other		40.3	35.7
Total Current Assets		294.5	371.0
Property, Plant and Equipment – Net		3,741.2	3,669.1
Regulatory Assets		359.6	372.0
Investment in ATC		135.6	124.5
Other Investments		55.6	74.6
Goodwill and Intangible Assets – Net		213.4	215.2
Other Non-Current Assets		106.5	68.1
Total Assets	[1]	4,906.4	4,894.5
Current Liabilities [Abstract]
Accounts Payable		74.0	88.8
Accrued Taxes		46.5	44.0
Accrued Interest		17.6	18.6
Long-Term Debt Due Within One Year		187.7	35.7
Notes Payable		0.0	1.6
Other		73.7	86.1
Total Current Liabilities		399.5	274.8
Long-Term Debt		1,370.4	1,556.7
Deferred Income Taxes		584.1	579.8
Regulatory Liabilities		125.8	105.0
Defined Benefit Pension and Other Postretirement Benefit Plans		210.9	206.8
Other Non-Current Liabilities		322.7	349.0
Total Liabilities		3,013.4	3,072.1
Commitments, Guarantees and Contingencies (Note 11)
ALLETE's Equity [Abstract]
Common Stock Without Par Value, 80.0 Shares Authorized, 49.6 and 49.1 Shares Issued and Outstanding		1,295.3	1,271.4
Accumulated Other Comprehensive Loss		(28.2)	(24.5)
Retained Earnings		625.9	573.3
Total ALLETE Equity		1,893.0	1,820.2
Non-Controlling Interest in Subsidiaries		0.0	2.2
Total Equity		1,893.0	1,822.4
Total Liabilities and Equity		$ 4,906.4	$ 4,894.5

[1] As a result of revised accounting guidance adopted in the first quarter of 2016, we reclassified unamortized debt issuance costs from Other Non-Current Assets to Long-Term Debt on the Consolidated Balance Sheet. Prior period segment assets have been reclassified to conform to the current presentation. (See Note 1. Operations and Significant Accounting Policies.)