Share-Based Payments Narrative (Details) shares in Millions	12 Months Ended
	Dec. 31, 2019 plan $ / shares shares	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 $ / shares shares
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Awards granted (in shares) | shares	0.5	0.4	0.3
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 55.03	$ 72.78	$ 92.02
DSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 56.68	$ 64.48	$ 86.06
Performance shares (PSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares) | shares	0.3	0.2	0.2
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 70.37	$ 86.85
Granted, weighted-average grant date fair value (in dollars per unit)	$ 53.31	$ 78.30	$ 97.13
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Annual Vesting Percentage	33.33%
Award vesting period	3 years
Awards granted (in shares) | shares	0.4	0.2	0.2
Granted, weighted-average grant date fair value (in dollars per unit)	$ 9.20	$ 15.44	$ 18.66
Terms of SBC award	10 years
Incentive Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based compensation plans | plan	1