NET EARNINGS PER SHARE - Potential Shares Not Included in the Computation of Diluted Earnings Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential shares not included in the computation of diluted earnings per share	1,351	1,462	5,016
Performance share units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential shares not included in the computation of diluted earnings per share	799	384	155
Preference shares(1)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential shares not included in the computation of diluted earnings per share	0	0	25,307