Contingencies	3 Months Ended
Jul. 31, 2013
Commitments And Contingencies Disclosure [Abstract]
Contingencies	6. CONTINGENCIES Legal Proceedings In the ordinary course of our business and as a result of the extensive governmental regulation of the solid waste industry, we are subject to various judicial and administrative proceedings involving state and local agencies. In these proceedings, an agency may seek to impose fines or to revoke or deny renewal of an operating permit held by us. From time to time, we may also be subject to actions brought by special interest or other groups, adjacent landowners or residents in connection with the permitting and licensing of landfills and transfer stations, or alleging environmental damage or violations of the permits and licenses pursuant to which we operate. In addition, we have been named defendants in various claims and suits pending for alleged damages to persons and property, alleged violations of certain laws and alleged liabilities arising out of matters occurring during the ordinary operation of the waste management business. In accordance with FASB ASC 450-20, we accrue for legal proceedings when losses become probable and reasonably estimable. As of the end of each applicable reporting period, we review each of our legal proceedings to determine whether it is probable, reasonably possible or remote that a liability has been incurred and, if it is at least reasonably possible, whether a range of loss can be reasonably estimated under the provisions of FASB ASC 450-20. In instances where we determine that a loss is probable and we can reasonably estimate a range of losses we may incur with respect to such a matter, we record an accrual for the amount within the range that constitutes our best estimate of the possible loss. If we are able to reasonably estimate a range but no amount within the range appears to be a better estimate than any other, we record an accrual in the amount that is the low end of such range. When a loss is reasonably possible, but not probable, we will not record an accrual but we will disclose our estimate of the possible range of loss where such estimate can be made in accordance with ASC 450-20. As of July 31, 2013, there were no accruals established related to our outstanding legal proceedings. *Environmental Liability* We are subject to liability for environmental damage, including personal injury and property damage, that our solid waste, recycling and power generation facilities may cause to neighboring property owners, particularly as a result of the contamination of drinking water sources or soil, possibly including damage resulting from conditions existing before we acquired the facilities. We may also be subject to liability for similar claims arising from off-site environmental contamination caused by pollutants or hazardous substances if we or our predecessors arrange or arranged to transport, treat or dispose of those materials. On December 20, 2000, the State of New York Department of Environmental Conservation (“DEC”) issued an Order on Consent (“Order”) which named Waste-Stream, Inc. (“WSI”), our subsidiary, General Motors Corporation (“GM”) and Niagara Mohawk Power Corporation (“NiMo”) as Respondents. The Order required that the Respondents undertake certain work on a 25-acre scrap yard and solid waste transfer station owned by WSI, including the preparation of a Remedial Investigation and Feasibility Study (“Study”). A draft of the Study was submitted to DEC in January 2009 (followed by a final report in May 2009). The Study estimated that the undiscounted costs associated with implementing the preferred remedies will be approximately $10,219. On February 28, 2011, the DEC issued a Proposed Remedial Action Plan for the site and accepted public comments on the proposed remedy through March 29, 2011. We submitted comments to the DEC on this matter. In April 2011, the DEC issued the final Record of Decision (“ROD”) for the site. The ROD was subsequently rescinded by the DEC for failure to respond to all submitted comments. The preliminary ROD, however, estimated that the present cost associated with implementing the preferred remedies would be approximately $12,130. The DEC issued the final ROD in June 2011 with proposed remedies consistent with its earlier ROD. A new Order on Consent and Administrative Settlement naming WSI and NiMo as Respondents was received by us on November 13, 2012, requiring that we enter into a Consent Order with DEC within 60 days and mandating implementation of the ROD. The deadline for execution of the Consent Order has been extended until September 30, 2013. It is unlikely that any costs relating to onsite remediation will be incurred until fiscal year 2015. WSI is jointly and severally liable for the total cost to remediate and we initially expected to be responsible for approximately 30% upon implementation of a cost-sharing agreement with NiMo and GM. Based on these estimates, we recorded an environmental remediation charge of $2,823 in the third quarter of fiscal year 2009. In the fourth quarter of fiscal year 2009, we recognized an additional charge of $1,532, representing an additional 15% of the estimated costs, in recognition of the deteriorating financial condition and eventual bankruptcy filing of GM. In the fourth quarter of fiscal year 2010, we recognized an additional charge of $335 based on changes in the expected timing of cash outflows. Based on the estimated costs in the ROD, and changes in the estimated timing of cash flows, we recorded an environmental remediation charge of $549 in the fourth quarter of fiscal year 2011. Such charges could be significantly higher if costs exceed estimates. We inflate these estimated costs in current dollars until the expected time of payment and discount the cost to present value using a risk free interest rate (2.70%). As of July 31, 2013 and April 30, 2013, we have recorded liabilities of $5,363 and $5,297, respectively, including the recognition of $34 of accretion expense in the three months ended July 31, 2013 and 2012, respectively. In September 2011, the DEC settled its environmental claim against the estate of the former GM (known as the “Motors Liquidation Trust”) for future remediation costs relating to the WSI site for face value of $3,000. In addition, in November 2011 we settled our own claim against the Motors Liquidation Trust for face value of $100. These claims will be paid by GM in warrants to obtain stock of the reorganized GM. We began receiving the warrants in May 2013 and expect the remainder of the warrants to be issued in fiscal year 2014. We have not assumed that any proceeds from the sale of securities received in payment of these claims will reduce our exposure.

6. CONTINGENCIES

Legal Proceedings

In the ordinary course of our business and as a result of the extensive governmental regulation of the solid waste industry, we are subject to various judicial and administrative proceedings involving state and local agencies. In these proceedings, an agency may seek to impose fines or to revoke or deny renewal of an operating permit held by us. From time to time, we may also be subject to actions brought by special interest or other groups, adjacent landowners or residents in connection with the permitting and licensing of landfills and transfer stations, or alleging environmental damage or violations of the permits and licenses pursuant to which we operate. In addition, we have been named defendants in various claims and suits pending for alleged damages to persons and property, alleged violations of certain laws and alleged liabilities arising out of matters occurring during the ordinary operation of the waste management business.

In accordance with FASB ASC 450-20, we accrue for legal proceedings when losses become probable and reasonably estimable. As of the end of each applicable reporting period, we review each of our legal proceedings to determine whether it is probable, reasonably possible or remote that a liability has been incurred and, if it is at least reasonably possible, whether a range of loss can be reasonably estimated under the provisions of FASB ASC 450-20. In instances where we determine that a loss is probable and we can reasonably estimate a range of losses we may incur with respect to such a matter, we record an accrual for the amount within the range that constitutes our best estimate of the possible loss. If we are able to reasonably estimate a range but no amount within the range appears to be a better estimate than any other, we record an accrual in the amount that is the low end of such range. When a loss is reasonably possible, but not probable, we will not record an accrual but we will disclose our estimate of the possible range of loss where such estimate can be made in accordance with ASC 450-20. As of July 31, 2013, there were no accruals established related to our outstanding legal proceedings.

Environmental Liability

We are subject to liability for environmental damage, including personal injury and property damage, that our solid waste, recycling and power generation facilities may cause to neighboring property owners, particularly as a result of the contamination of drinking water sources or soil, possibly including damage resulting from conditions existing before we acquired the facilities. We may also be subject to liability for similar claims arising from off-site environmental contamination caused by pollutants or hazardous substances if we or our predecessors arrange or arranged to transport, treat or dispose of those materials.

On December 20, 2000, the State of New York Department of Environmental Conservation (“DEC”) issued an Order on Consent (“Order”) which named Waste-Stream, Inc. (“WSI”), our subsidiary, General Motors Corporation (“GM”) and Niagara Mohawk Power Corporation (“NiMo”) as Respondents. The Order required that the Respondents undertake certain work on a 25-acre scrap yard and solid waste transfer station owned by WSI, including the preparation of a Remedial Investigation and Feasibility Study (“Study”). A draft of the Study was submitted to DEC in January 2009 (followed by a final report in May 2009). The Study estimated that the undiscounted costs associated with implementing the preferred remedies will be approximately $10,219. On February 28, 2011, the DEC issued a Proposed Remedial Action Plan for the site and accepted public comments on the proposed remedy through March 29, 2011. We submitted comments to the DEC on this matter. In April 2011, the DEC issued the final Record of Decision (“ROD”) for the site. The ROD was subsequently rescinded by the DEC for failure to respond to all submitted comments. The preliminary ROD, however, estimated that the present cost associated with implementing the preferred remedies would be approximately $12,130. The DEC issued the final ROD in June 2011 with proposed remedies consistent with its earlier ROD. A new Order on Consent and Administrative Settlement naming WSI and NiMo as Respondents was received by us on November 13, 2012, requiring that we enter into a Consent Order with DEC within 60 days and mandating implementation of the ROD. The deadline for execution of the Consent Order has been extended until September 30, 2013. It is unlikely that any costs relating to onsite remediation will be incurred until fiscal year 2015.

WSI is jointly and severally liable for the total cost to remediate and we initially expected to be responsible for approximately 30% upon implementation of a cost-sharing agreement with NiMo and GM. Based on these estimates, we recorded an environmental remediation charge of $2,823 in the third quarter of fiscal year 2009. In the fourth quarter of fiscal year 2009, we recognized an additional charge of $1,532, representing an additional 15% of the estimated costs, in recognition of the deteriorating financial condition and eventual bankruptcy filing of GM. In the fourth quarter of fiscal year 2010, we recognized an additional charge of $335 based on changes in the expected timing of cash outflows. Based on the estimated costs in the ROD, and changes in the estimated timing of cash flows, we recorded an environmental remediation charge of $549 in the fourth quarter of fiscal year 2011. Such charges could be significantly higher if costs exceed estimates. We inflate these estimated costs in current dollars until the expected time of payment and discount the cost to present value using a risk free interest rate (2.70%). As of July 31, 2013 and April 30, 2013, we have recorded liabilities of $5,363 and $5,297, respectively, including the recognition of $34 of accretion expense in the three months ended July 31, 2013 and 2012, respectively.

In September 2011, the DEC settled its environmental claim against the estate of the former GM (known as the “Motors Liquidation Trust”) for future remediation costs relating to the WSI site for face value of $3,000. In addition, in November 2011 we settled our own claim against the Motors Liquidation Trust for face value of $100. These claims will be paid by GM in warrants to obtain stock of the reorganized GM. We began receiving the warrants in May 2013 and expect the remainder of the warrants to be issued in fiscal year 2014. We have not assumed that any proceeds from the sale of securities received in payment of these claims will reduce our exposure.