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Asset Retirement Obligations | 12 Months Ended
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Dec. 31, 2020
Asset Retirement Obligation [Abstract] |
Asset Retirement Obligations | Asset Retirement ObligationsWe have recognized asset retirement obligations associated with various legal obligations including costs to remove and dispose of certain construction materials located within many of our facilities, certain costs to retire pipeline, removal costs for certain underground storage tanks, removal of certain pipelines known to contain PCB contamination, closure costs for certain sites including ash ponds, solid waste management units and a landfill, as well as some other nominal asset retirement obligations. We also have an obligation associated with the decommissioning of our two hydro facilities located in Indiana. These hydro facilities have an indeterminate life, and as such, no asset retirement obligation has been recorded. Changes in our liability for asset retirement obligations for the years 2020 and 2019 are presented in the table below:
(in millions) | 2020 |  | 2019 |
Beginning Balance | $ | 416.9 |  |  | $ | 352.0 |  |
Accretion recorded as a regulatory asset/liability | 17.3 |  |  | 15.7 |  |
Additions | 5.5 |  |  | — |  |
Settlements | (13.9) |  |  | (5.4) |  |
Change in estimated cash flows | 86.0 |  | (1) | 54.6 |  | (2)
Other | (16.2) |  | (3) | — |  |
Ending Balance | $ | 495.6 |  |  | $ | 416.9 |  |
(1)The change in estimated cash flows for 2020 is primarily attributed to revisions to the estimated costs associated with refining the CCR compliance plan, changes in estimated costs for electric generating stations and the changes in estimated costs for retirement of gas mains. See Note 20-D. "Environmental Matters" for additional information on CCRs. (2)The change in estimated cash flows for 2019 is primarily attributed to changes in estimated costs and settlement timing for electric generating stations and the changes in estimated costs for retirement of gas mains. (3)Represents the Columbia of Massachusetts Asset Retirement Obligations that were included in the sale of the Massachusetts Business that occurred on October 9, 2020. Certain non-legal costs of removal that have been, and continue to be, included in depreciation rates and collected in the customer rates of the rate-regulated subsidiaries are classified as "Regulatory liabilities" on the Consolidated Balance Sheets.

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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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -URI http://asc.fasb.org/subtopic&trid=2175671 + Details
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