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Related Party Transactions - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Apr. 30, 2014 Lease | Apr. 30, 2013 | Apr. 30, 2012
Related Party Transaction [Line Items] |  |  |
Total services purchased | $ 7,816 | $ 6,577 | $ 2,612
Outstanding accounts payable | 890 | 1,189 |
Number of leases | 2 |  |
Capital lease expiration date | Apr. 30, 2023 |  |
Total expense charged to operations under lease agreement | 386 | 286 | 300
Landfill post-closure cost | 2,376 | 2,491 |
Accrued costs associated with post-closure obligations | 44,654 | 43,170 | 39,629
Loan to an employee outstanding |  | 147 |
Landfills [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Landfill owned | 2 |  |
Landfill post-closure cost | 8 | 8 | 8
Accrued costs associated with post-closure obligations | 94 | 100 |
Related Party [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Leases monthly payments | 27 |  |
Allowance for Notes Receivable [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Charges in general and administration to reserve for the notes | $ 149 |  |

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- Definition Landfills owned by major stockholders. + References No definition available. + Details
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- Definition Number of related party capital lease agreements entered into. + References No definition available. + Details
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- Definition Charges to reserve for the notes. + References No definition available. + Details
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- Definition Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(k)(1)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph k -Subparagraph 1 -Article 4 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph a -Article 5 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 + Details
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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement 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 -Subparagraph (c) -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 -Glossary Asset Retirement Obligation -URI http://asc.fasb.org/extlink&oid=6505190 + Details
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