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v3.3.1.900

Property, Plant and Equipment (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014
Property, Plant and Equipment [Line Items] |  |  |  |  |
Construction Work in Progress | [1] | $ 0.0 |  | $ 48.2 |
Property, Plant and Equipment – Net |  | 3,669.1 |  | 3,284.8 |
Asset Retirement Obligation [Roll Forward] |  |  |  |  |
Beginning Obligation |  | 109.2 |  | 81.8 |
Accretion |  | 7.3 |  | 5.5 |
Liabilities Recognized |  | 5.1 | [2] | 23.0 | [3]
Liabilities Settled |  | (2.6) |  | (0.5) |
Revisions in Estimated Cash Flows |  | 12.4 |  | (0.6) |
Ending Obligation |  | 131.4 |  | 109.2 |
Regulated Operations [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Property, Plant and Equipment |  | 4,336.7 |  | 3,903.3 |
Construction Work in Progress |  | 101.2 |  | 355.4 |
Accumulated Depreciation |  | (1,323.8) |  | (1,260.2) |
Property, Plant and Equipment – Net |  | $ 3,114.1 |  | 2,998.5 |
Regulated Operations [Member] | Generation [Member] | Minimum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 10 years |  |  |
Regulated Operations [Member] | Generation [Member] | Maximum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 50 years |  |  |
Regulated Operations [Member] | Transmission [Member] | Minimum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 44 years |  |  |
Regulated Operations [Member] | Transmission [Member] | Maximum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 67 years |  |  |
Regulated Operations [Member] | Distribution [Member] | Minimum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 18 years |  |  |
Regulated Operations [Member] | Distribution [Member] | Maximum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 65 years |  |  |
ALLETE Clean Energy [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Property, Plant and Equipment |  | $ 467.3 |  | 203.7 |
Construction Work in Progress |  | 4.0 |  | 1.3 |
Accumulated Depreciation |  | (24.0) |  | (8.4) |
Property, Plant and Equipment – Net |  | $ 447.3 |  | 196.6 |
ALLETE Clean Energy [Member] | Minimum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 5 years |  |  |
ALLETE Clean Energy [Member] | Maximum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 44 years |  |  |
U.S. Water Services [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Property, Plant and Equipment |  | $ 15.6 |  | 0.0 |
Accumulated Depreciation |  | (3.4) |  | 0.0 |
Property, Plant and Equipment – Net |  | $ 12.2 |  | 0.0 |
U.S. Water Services [Member] | Minimum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 3 years |  |  |
U.S. Water Services [Member] | Maximum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 39 years |  |  |
Corporate and Other [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Property, Plant and Equipment | [4] | $ 165.6 |  | 152.5 |
Construction Work in Progress |  | 4.5 |  | 4.6 |
Accumulated Depreciation |  | (74.6) |  | (67.4) |
Property, Plant and Equipment – Net |  | $ 95.5 |  | $ 89.7 |
Corporate and Other [Member] | Minimum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 3 years |  |  |
Corporate and Other [Member] | Maximum [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Estimated Useful Lives |  | 39 years |  |  |
[1] | Construction Costs for Development Project related to ALLETE Clean Energy’s project to construct a wind energy facility which was sold in 2015. (See Note 7. Acquisitions.)
[2] | The increase in 2015 is related to the ALLETE Clean Energy wind energy facilities acquisitions in 2015. (See Note 7. Acquisitions.)
[3] | The increase in 2014 is related to BNI Energy for coal mining expansion and ALLETE Clean Energy due to wind energy facilities acquisitions.(See Note 7. Acquisitions.)
[4] | Primarily includes BNI Energy and a small amount of non-rate base generation.

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- Definition Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.14) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Asset Retirement Obligation -URI http://asc.fasb.org/extlink&oid=6505190 + Details
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