Long Term Debt - Additional Information (Detail) (CAD) In Millions, unless otherwise specified	3 Months Ended
Sep. 30, 2013 Stand-by long term credit facility	Mar. 31, 2013 Stand-by long term credit facility	Dec. 31, 2012 Stand-by long term credit facility	Dec. 31, 2013 Floating Rate Loan Facility Exxon Mobil	Jan. 31, 2014 Subsequent Event Floating Rate Loan Facility Exxon Mobil
Line of Credit Facility [Line Items]
Debt instrument, maturity date	Aug. 31, 2015
Line of Credit maximum borrowing capacity		500	300	5,000	6,250

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant