Stock-Based Compensation (Summary Of Restricted Stock Units And Phantom Stock Awards) (Details) (USD $) In Thousands, except Per Share data	6 Months Ended
	Jun. 30, 2011
Restricted Shares [Member]
Non-vested shares outstanding at December 31, 2010	178
Granted, shares	195
Vested, shares	(10)
Forfeited, shares	(14)
Non-vested shares outstanding at June 30, 2011	349
Non-vested shares outstanding, weighted-average grant date fair value	$ 17.17
Granted, weighted-average grant date fair value	$ 18.57
Vested, weighted-average grant date fair value	$ 17.54
Forfeited, weighted-average grant date fair value	$ 17.57
Non-vested shares outstanding, weighted-average grant date fair value	$ 17.92
Restricted Stock Units And Phantom Stock [Member]
Non-vested shares outstanding at December 31, 2010	47
Granted, shares	86
Forfeited, shares	(5)
Non-vested shares outstanding at June 30, 2011	128
Non-vested shares outstanding, weighted-average grant date fair value	$ 17.05
Granted, weighted-average grant date fair value	$ 17.77
Forfeited, weighted-average grant date fair value	$ 17.61
Non-vested shares outstanding, weighted-average grant date fair value	$ 17.51
Performance Based Restricted Stock Units [Member]
Non-vested shares outstanding at December 31, 2010
Granted, shares	93	[1]
Forfeited, shares
Non-vested shares outstanding at June 30, 2011	93
Non-vested shares outstanding, weighted-average grant date fair value
Granted, weighted-average grant date fair value	$ 18.57	[1]
Forfeited, weighted-average grant date fair value
Non-vested shares outstanding, weighted-average grant date fair value	$ 18.57

[1] Represents target number of shares that can vest based on the achievement of certain performance criteria