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Financial instruments and risk management - Risk management (Details)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Concentration Risk [Line Items]
General payment terms	30 days
Trade accounts receivables | Geographic concentration risk | Western Canada
Concentration Risk [Line Items]
Concentration risk, percentage	100.00%	95.00%
Customer A | Total revenues | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	25.00%	15.00%	30.00%
Customer A | Accounts receivable and unbilled revenue | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	23.00%	4.00%
Customer B | Total revenues | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	23.00%	23.00%	10.00%
Customer B | Accounts receivable and unbilled revenue | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	20.00%	31.00%
Customer C | Total revenues | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	17.00%	6.00%	0.00%
Customer C | Accounts receivable and unbilled revenue | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%	10.00%
Customer D | Total revenues | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	8.00%	10.00%	13.00%
Customer D | Accounts receivable and unbilled revenue | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%	4.00%
Customer E | Total revenues | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	6.00%	31.00%	38.00%
Customer E | Accounts receivable and unbilled revenue | Major customers
Concentration Risk [Line Items]
Concentration risk, percentage	8.00%	11.00%

X

- Definition

Accounts Receivable, General Payment Terms

+ References

No definition available.

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- Details

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X

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 18

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13537-108611



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13531-108611

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