Incentive Plans (Summary of Additional Stock Option Information) (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)	392,300
Options outstanding, average remaining life (in years)	4 years 3 months 18 days
Options exercisable (in shares)	174,300
Options exercisable, average remaining life (in years)	3 years
$39.46 to $49.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Lower range limit of exercise price (in dollars per share) | $ / shares	$ 39.46
Upper range limit of exercise price (in dollars per share) | $ / shares	$ 49.99
Options outstanding (in shares)	3,900
Options outstanding, average remaining life (in years)	1 year 1 month 6 days
Options exercisable (in shares)	3,900
Options exercisable, average remaining life (in years)	1 year 1 month 6 days
$50.00 to $59.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Lower range limit of exercise price (in dollars per share) | $ / shares	$ 50.00
Upper range limit of exercise price (in dollars per share) | $ / shares	$ 59.99
Options outstanding (in shares)	71,000
Options outstanding, average remaining life (in years)	3 years 1 month 6 days
Options exercisable (in shares)	71,000
Options exercisable, average remaining life (in years)	3 years 1 month 6 days
$60.00 to $69.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Lower range limit of exercise price (in dollars per share) | $ / shares	$ 60.00
Upper range limit of exercise price (in dollars per share) | $ / shares	$ 69.99
Options outstanding (in shares)	90,550
Options outstanding, average remaining life (in years)	4 years 1 month 6 days
Options exercisable (in shares)	43,550
Options exercisable, average remaining life (in years)	4 years 1 month 6 days
$70.00 to $79.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Lower range limit of exercise price (in dollars per share) | $ / shares	$ 70.00
Upper range limit of exercise price (in dollars per share) | $ / shares	$ 79.99
Options outstanding (in shares)	226,850
Options outstanding, average remaining life (in years)	4 years 9 months 18 days
Options exercisable (in shares)	55,850
Options exercisable, average remaining life (in years)	2 years 1 month 6 days