INTERIM CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (unaudited) - CAD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 348	$ 431
Net (loss) gain in foreign currency translation adjustments, net of hedging activities	(20)	5
Change in derivatives designated as cash flow hedges	21	5
Change in pension and post-retirement defined benefit plans	29	38
Other comprehensive income (loss) before income taxes	30	48
Income tax (expense) recovery on above items	6	(18)
Other comprehensive income (loss)	36	30
Comprehensive income	$ 384	$ 461