Share-Based Compensation Plans - Shares Granted and Weighted Average Fair Value Per Share (Details) - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted, options (in shares)	163	122
Weighted-average per share fair value, options (in dollars per share)	$ 17.78	$ 31.46
Total shares granted, options and non-options (in shares)	522	363
Weighted-average per share value, options and non-options (in dollars per share)	$ 58.96	$ 88.76
Deferred Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted, non-options (in shares)	20	10
Weighted-average per share fair value, non-options (in dollars per share)	$ 64.80	$ 126.11
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted, non-options (in shares)	203	137
Weighted-average per share fair value, non-options (in dollars per share)	$ 78.90	$ 117.60
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted, non-options (in shares)	136	94
Weighted-average per share fair value, non-options (in dollars per share)	$ 77.70	$ 117.19