Incentive Plan (Summary Of Incentive Award Plan's Stock Option) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012
Incentive Plan [Abstract]
Options outstanding, beginning of period, Shares	337,760
Exercised, Shares	(32,758)
Cancelled / Forfeited, Shares
Options outstanding, end of period, Shares	305,002
Exercisable, end of period, Shares	293,751
Options outstanding, beginning of period, Weighted average exercise price	$ 24.17
Exercised, Weighted average exercise price	$ 39.62
Options outstanding, end of period, Weighted average exercise price	$ 22.51
Exercisable, end of period, Weighted average exercise price	$ 21.78