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Property, Plant and Equipment | 12 Months Ended
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Dec. 31, 2012
Property, Plant and Equipment [Abstract] |
Property, Plant and Equipment [Text Block] | PROPERTY, PLANT AND EQUIPMENT
Property, Plant and Equipment |  |  |
As of December 31 | 2012 |  | 2011
Millions |  |  |
Regulated Utility |  | $3,232.9 |  |  |  | $2,794.8 |
Construction Work in Progress | 151.8 |  |  | 155.0 |
Accumulated Depreciation | (1,102.8 | ) |  | (1,024.6 | )
Regulated Utility Plant - Net | 2,281.9 |  |  | 1,925.2 |
Non-Rate Base Energy Operations | 118.0 |  |  | 106.4 |
Construction Work in Progress | 4.2 |  |  | 2.3 |
Accumulated Depreciation | (56.7 | ) |  | (51.4 | )
Non-Rate Base Energy Operations Plant - Net | 65.5 |  |  | 57.3 |
Other Plant - Net | 0.2 |  |  | 0.2 |
Property, Plant and Equipment - Net |  | $2,347.6 |  |  |  | $1,982.7 |
Depreciation is computed using the straight-line method over the estimated useful lives of the various classes of assets.
Estimated Useful Lives of Property, Plant and Equipment
Regulated Utility – | Generation | 3 to 35 years | Non-Rate Base Operations | 3 to 61 years
| Transmission | 42 to 61 years | Other Plant | 5 to 25 years
| Distribution | 14 to 65 years |  |
Asset Retirement Obligations. We recognize, at fair value, obligations associated with the retirement of certain tangible, long-lived assets that result from the acquisition, construction or development and/or normal operation of the asset. Asset retirement obligations (ARO) relate primarily to the decommissioning of our coal-fired and wind generating facilities and land reclamation at BNI Coal, and are included in other non-current liabilities on our Consolidated Balance Sheet. The associated retirement costs are capitalized as part of the related long-lived asset and depreciated over the useful life of the asset. Removal costs associated with certain distribution and transmission assets have not been recognized, as these facilities have indeterminate useful lives. Conditional asset retirement obligations have been identified for treated wood poles and remaining polychlorinated biphenyl and asbestos-containing assets; however, removal costs have not been recognized because they are considered immaterial to our consolidated financial statements. Long-standing ratemaking practices approved by applicable state and federal regulatory commissions have allowed provisions for future plant removal costs in depreciation rates. These plant removal cost recoveries are classified either as AROs or as a regulatory liability for non-ARO obligations. To the extent annual accruals for plant removal costs differ from accruals under approved depreciation rates, a regulatory asset has been established in accordance with the guidance for AROs. (See Note 5. Regulatory Matters.)
Asset Retirement Obligation |  |
Millions |  |
Obligation as of December 31, 2010 |  |  | $50.3 |
Accretion Expense |  | 6.4 |
Additional Liabilities Incurred in 2011 |  | 0.3 |
Obligation as of December 31, 2011 |  | 57.0 |
Accretion Expense |  | 3.8 |
Additional Liabilities Incurred in 2012 |  | 17.1 |
Obligation as of December 31, 2012 |  |  | $77.9 |

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- Definition The entire disclosure for long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software. This disclosure may include property plant and equipment accounting policies and methodology, a schedule of property, plant and equipment gross, additions, deletions, transfers and other changes, depreciation, depletion and amortization expense, net, accumulated depreciation, depletion and amortization expense and useful lives, income statement disclosures, assets held for sale and public utility disclosures. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760 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 210.5-02.13-14) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: 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 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2921-110230 + Details
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