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Asset Retirement Obligations | 6 Months Ended
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Jun. 30, 2013
Asset Retirement Obligation [Abstract] |
Asset Retirement Obligations | Asset Retirement Obligations Certain costs of removal that have been, and continue to be, included in depreciation rates and collected in the service rates of the rate-regulated subsidiaries are classified as “Regulatory liabilities and other removal costs” on the Condensed Consolidated Balance Sheets (unaudited). Changes in NiSource’s liability for asset retirement obligations for the six months ended June 30, 2013 and 2012 are presented in the table below:
(in millions) | 2013 |  | 2012
Balance as of January 1, | $ | 160.4 |  |  | $ | 146.4 |
Accretion expense | 0.6 |  |  | 0.5 |
Accretion recorded as a regulatory asset/liability | 4.4 |  |  | 4.3 |
Additions | 3.0 |  |  | — |
Settlements | (0.6 | ) |  | (1.5 | )
Change in estimated cash flows | (0.7 | ) |  | — |
Balance as of June 30, | $ | 167.1 |  |  | $ | 149.7 |

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- Definition The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service 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 -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 -Topic 410 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7569-110849 + Details
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