Incentive Plans (Additional Information about Stock Options Outstanding) (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding	5,443,288
Options Outstanding, Avg. Life Remaining in Years	3 years 4 months 24 days
Options Exercisable	3,542,352
Options Exercisable, Avg. Life Remaining in Years	2 years 4 months 24 days
Range of Exercise Prices per Option $37.44 to $45.48 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit | $ / shares	$ 37.44
Range of exercise prices, upper limit | $ / shares	$ 45.48
Options Outstanding	771,906
Options Outstanding, Avg. Life Remaining in Years	10 months 24 days
Options Exercisable	771,906
Options Exercisable, Avg. Life Remaining in Years	10 months 24 days
Range of Exercise Prices per Option $49.65 to $51.63 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit | $ / shares	$ 49.65
Range of exercise prices, upper limit | $ / shares	$ 51.63
Options Outstanding	2,067,449
Options Outstanding, Avg. Life Remaining in Years	4 years 3 months 18 days
Options Exercisable	1,219,449
Options Exercisable, Avg. Life Remaining in Years	3 years
Range of Exercise Prices per Option $54.21 to $62.98 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit | $ / shares	$ 54.21
Range of exercise prices, upper limit | $ / shares	$ 62.98
Options Outstanding	2,603,933
Options Outstanding, Avg. Life Remaining in Years	3 years 6 months
Options Exercisable	1,550,997
Options Exercisable, Avg. Life Remaining in Years	2 years 8 months 12 days