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Other assets - Intangible assets (Details) (CAD) | 12 Months Ended
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Mar. 31, 2013 | Mar. 31, 2012 | Mar. 31, 2011
Finite-Lived Intangible Assets [Line Items] |  |  |
Cost | 22,264,000 | 25,648,000 |
Accumulated Amortization | 13,639,000 | 12,782,000 |
Net Book Value | 8,625,000 | 12,866,000 |
Internally developed computer software capitalized during the period | 5,081,000 | 3,537,000 | 4,748,000
Amortization of intangible assets | 3,694,000 | 4,287,000 | 2,150,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] |  |  |
2014 | 3,430,000 |  |
2015 | 2,612,000 |  |
2016 | 1,801,000 |  |
2017 | 782,000 |  |
2018 and thereafter | 0 |  |
Net Book Value | 8,625,000 | 12,866,000 |
Customer relationships and backlog |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Cost |  | 4,442,000 |
Accumulated Amortization |  | 1,445,000 |
Net Book Value |  | 2,997,000 |
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] |  |  |
Net Book Value |  | 2,997,000 |
Other intangible assets |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Cost | 350,000 | 2,364,000 |
Accumulated Amortization | 328,000 | 1,204,000 |
Net Book Value | 22,000 | 1,160,000 |
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] |  |  |
Net Book Value | 22,000 | 1,160,000 |
Internal-use software |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Cost | 21,914,000 | 16,825,000 |
Accumulated Amortization | 13,311,000 | 9,644,000 |
Net Book Value | 8,603,000 | 7,181,000 |
Impairment of intangible assets | 0 | 249,000 | 0
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] |  |  |
Net Book Value | 8,603,000 | 7,181,000 |
Patents |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Cost |  | 2,017,000 |
Accumulated Amortization |  | 489,000 |
Net Book Value |  | 1,528,000 |
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] |  |  |
Net Book Value |  | 1,528,000 |

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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 45 -Subparagraph a(2) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=7658586&loc=d3e16323-109275 + Details
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- Definition Amount of amortization expense expected to be recognized during the next fiscal year following the latest fiscal year for assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=7658586&loc=d3e16323-109275 + Details
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