Pensions and other postretirement benefits (Details 5) (CAD) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Pensions [Member]
Amounts Recognized In Accumulated Other Comprehensive Loss [Line Items]
Net actuarial gain (loss)	(2,720)	(1,185)
Prior service cost	(30)	(5)
Other Postretirement Benefit Plans Defined Benefit [Member]
Amounts Recognized In Accumulated Other Comprehensive Loss [Line Items]
Net actuarial gain (loss)	3	1
Prior service cost	(3)	(4)

The pretax net amount of gains and losses that are not yet recognized as a component of net periodic benefit cost, and that are recognized as increases or decreases in other comprehensive income as they arise. Gains and losses are due to changes in the value of either the benefit obligation or the plan assets resulting from experience different from that assumed or from a change in an actuarial assumption, or the consequence of a decision to temporarily deviate from the substantive plan.

+ References+ Details

Amount related to the pretax cost of benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation, which has not yet been recognized as components of net periodic benefit cost.

+ References

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

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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+ Details