Pensions and other postretirement benefits (Details 9) (CAD) In Millions, unless otherwise specified	Dec. 31, 2011
Pensions [Member]
Estimated future benefit payments [Line Items]
2012	973
2013	996
2014	1,018
2015	1,040
2016	1,060
Years 2017 to 2021	5,444
Other Postretirement Benefit Plans Defined Benefit [Member]
Estimated future benefit payments [Line Items]
2012	18
2013	18
2014	19
2015	19
2016	19
Years 2017 to 2021	98

The amount of the aggregate benefits expected to be paid in the five fiscal years thereafter (the aggregate amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsInFiveFiscalYearsThereafter
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant