Employee Incentive Plans Employee Incentive Plans, Weighted Average Grant Date Fair Value (Details) - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value per share (in dollars per share)	$ 73.14	$ 74.49
CP-Based Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value per share (in dollars per share)	79.69	80.46
TSR-Based Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value per share (in dollars per share)	97.88	93.02
EVA - Based Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value per share (in dollars per share)	$ 79.69	$ 0.00