Shareholders Equity (Schedule Of Changes In Non-Vested Restricted Shares) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Shareholders' Equity
Non-vested shares at beginning of period, Number of Shares	732,412	664,909	466,387
Non-vested shares at end of period, Weighted Average Grant Price	$ 21.91	$ 22.16	$ 22.29
Shares granted, Number of Shares	281,429	276,869	233,460
Shares granted, Weighted Average Grant Price	$ 26.78	$ 21.78	$ 21.83
Shares vested, net of shares repurchased to cover tax withholding requirements,, Number of Shares	(183,019)	(208,949)	(8,973)
Shares vested, net of shares repurchased to cover tax withholding requirements, , Weighted Average Grant Price	$ 25.98	$ 23.11	$ 20.45
Shares forfeited, Number of Shares	(2,136)	(417)	(25,965)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 26.26	$ 24.75	$ 22.21
Non-vested shares at end of period, Number of Shares	828,686	732,412	664,909
Non-vested shares at end of period, Weighted Average Grant Price	$ 22.50	$ 21.91	$ 22.16