Stock-Based Compensation (Summary Of Restricted Stock Activity) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Time-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, beginning of period, Shares	768,529	838,129
Granted, Shares	168,750	95,503
Vested, Shares	(117,522)	(185,253)
Forfeited, Shares	(10,309)	(4,380)
Outstanding, end of period, Shares	809,448	743,999
Outstanding, beginning of period, Weighted Average Grant Date Fair Value	$ 40.17	$ 40.93
Granted, Weighted Average Grant Date Fair Value	$ 36.93	$ 46.49
Vested, Weighted Average Grant Date Fair Value	$ 35.27	$ 45.13
Forfeited, Weighted Average Grant Date Fair Value	$ 39.67	$ 45.67
Outstanding, end of period, Weighted Average Grant Date Fair Value	$ 40.21	$ 40.57
Performance And Market-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, beginning of period, Shares	69,500	101,680
Granted, Shares	99,500	42,500
Vested, Shares		(25,055)
Forfeited, Shares
Outstanding, end of period, Shares	169,000	119,125
Outstanding, beginning of period, Weighted Average Grant Date Fair Value	$ 45.37	$ 39.62
Granted, Weighted Average Grant Date Fair Value	$ 36.61	$ 46.47
Vested, Weighted Average Grant Date Fair Value		$ 45.21
Forfeited, Weighted Average Grant Date Fair Value
Outstanding, end of period, Weighted Average Grant Date Fair Value	$ 40.21	$ 40.89