Incentive Plan (Summary Of Stock Options Outstanding And Exercisable) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number outstanding	122,773	123,690
Weighted average remaining contractual life (years), Outstanding	2 years 1 month 24 days
Weighted average exercise price, Outstanding	$ 30.04
Aggregate intrinsic value, Outstanding	$ 2,828,506
$12.00-13.02 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower limit	$ 12.00
Exercise price, upper limit	$ 13.02
Number outstanding	34,870
Weighted average remaining contractual life (years), Outstanding	6 months 29 days
Weighted average exercise price, Outstanding	$ 12.00
Aggregate intrinsic value, Outstanding	1,432,460
$20.37-28.09 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower limit	$ 20.37
Exercise price, upper limit	$ 28.09
Number outstanding	17,000
Weighted average remaining contractual life (years), Outstanding	1 year 7 months 21 days
Weighted average exercise price, Outstanding	$ 21.28
Aggregate intrinsic value, Outstanding	540,630
$33.18-41.73 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower limit	$ 33.18
Exercise price, upper limit	$ 41.73
Number outstanding	70,903
Weighted average remaining contractual life (years), Outstanding	3 years 18 days
Weighted average exercise price, Outstanding	$ 41.02
Aggregate intrinsic value, Outstanding	$ 855,416