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Goodwill and Intangible Assets - Schedule of Activity and Balances Related to Goodwill (Detail) (USD $) In Thousands, unless otherwise specified | 6 Months Ended
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Oct. 31, 2013
Goodwill And Intangible Assets [Line Items] |
Goodwill, beginning balance | $ 115,928
Acquisitions | 2,329
Goodwill, ending balance | 118,257
Eastern Region [Member] |
Goodwill And Intangible Assets [Line Items] |
Goodwill, beginning balance | 16,858
Acquisitions | 133
Goodwill, ending balance | 16,991
Western Region [Member] |
Goodwill And Intangible Assets [Line Items] |
Goodwill, beginning balance | 86,880
Acquisitions | 467
Goodwill, ending balance | 87,347
Recycling [Member] |
Goodwill And Intangible Assets [Line Items] |
Goodwill, beginning balance | 12,190
Acquisitions |
Goodwill, ending balance | 12,190
Other [Member] |
Goodwill And Intangible Assets [Line Items] |
Goodwill, beginning balance |
Acquisitions | 1,729
Goodwill, ending balance | $ 1,729

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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266 + Details
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- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267 + Details
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