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Accrued Capping, Closure and Post Closure (Tables) | 3 Months Ended
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Jul. 31, 2013
Asset Retirement Obligation Disclosure [Abstract] |
Changes to Accrued Capping, Closure and Post-Closure Liabilities | The changes to accrued capping, closure and post-closure liabilities for the three months ended July 31, 2013 and 2012 are as follows:
|  | Three Months Ended July 31, |
|  | 2013 |  |  | 2012 |
Beginning balance |  | $ | 43,170 |  |  | $ | 39,629 |
Obligations incurred |  |  | 877 |  |  |  | 1,084 |
Accretion expense |  |  | 1,011 |  |  |  | 899 |
Payments |  |  | (309 | ) |  |  | (1,119 | )
Ending balance |  | $ | 44,749 |  |  | $ | 40,493 |

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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 + Details
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