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Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment and Estimated Useful Lives of Property, Plant and Equipment [Table Text Block]

Property, Plant and Equipment
As of December 31	2017				2016
Millions
Regulated Operations
Property, Plant and Equipment in Service		$4,523.7				$4,437.0
Construction Work in Progress	121.6				84.2
Accumulated Depreciation	(1,520.5		)		(1,426.1		)
Regulated Operations – Net	3,124.8				3,095.1
ALLETE Clean Energy
Property, Plant and Equipment in Service	482.5				472.3
Construction Work in Progress	144.9				101.0
Accumulated Depreciation	(60.8		)		(41.0		)
ALLETE Clean Energy – Net	566.6				532.3
U.S. Water Services
Property, Plant and Equipment in Service	24.8				19.5
Accumulated Depreciation	(10.4		)		(6.9		)
U.S. Water Services – Net	14.4				12.6
Corporate and Other (a)
Property, Plant and Equipment in Service	204.7				179.8
Construction Work in Progress	5.0				2.8
Accumulated Depreciation	(93.1		)		(81.4		)
Corporate and Other – Net	116.6				101.2
Property, Plant and Equipment – Net		$3,822.4				$3,741.2

(a) Primarily includes BNI Energy and a small amount of non-rate base generation.

Estimated Useful Lives of Property, Plant and Equipment
Regulated Operations			ALLETE Clean Energy (a)	5 to 35 years
Generation	5 to 50 years		U.S. Water Services	3 to 39 years
Transmission	44 to 67 years		Corporate and Other	3 to 50 years
Distribution	18 to 65 years

(a) ALLETE Clean Energy’s Property, Plant and Equipment consists primarily of WTGs with estimated useful lives ranging from 30 years to 35 years.

Asset Retirement Obligations [Table Text Block]

Asset Retirement Obligations
Millions
Obligation as of December 31, 2015			$131.4
Accretion		8.0
Liabilities Settled		(6.5		)
Revisions in Estimated Cash Flows		3.7
Obligation as of December 31, 2016		136.6
Accretion		7.6
Liabilities Settled		(5.9		)
Revisions in Estimated Cash Flows		(15.6		)
Obligation as of December 31, 2017			$122.7

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- References

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- Definition

Tabular disclosure of physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-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(13))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859

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