Income Taxes - Narrative (Details) - CAD	3 Months Ended		12 Months Ended
	Jun. 30, 2015	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Unrecognized tax benefits from capital losses			CAD 0	CAD 0
Less: Income tax (recovery) expense	CAD 23,000,000	CAD 7,000,000	607,000,000	562,000,000	CAD 250,000,000
Income tax operating losses carried forward			35,000,000
Minimum tax credits			1,000,000
Total amount of accrued interest and penalties			(4,000,000)	(1,000,000)	1,000,000
The total amount of accrued interest and penalties associated with unrecognized tax benefit			CAD 9,000,000	CAD 5,000,000	CAD 4,000,000