CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, shares authorized without par value (shares)	Unlimited	Unlimited
Common stock, par value (in CAD per share)	$ 0	$ 0
Common stock, shares issued (shares)	140,500,000	144,900,000
Common stock, shares outstanding (shares)	140,500,000	144,900,000
First preferred stock, shares authorized (shares)	Unlimited	Unlimited
Second preferred stock, shares authorized (shares)	Unlimited	Unlimited
First preferred stock, shares outstanding (shares)	0	0
Second preferred stock, shares outstanding (shares)	0	0