Stock-Based Compensation Expense (Schedule Of Non-Performance Based Restricted Stock) (Details) (Restricted Stock [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, beginning of period	333,416	535,625	536,700
Granted	63,600	92,750	88,625
Vested	(159,751)	(250,126)	(69,700)
Forfeited	(9,000)	(44,833)	(20,000)
Nonvested, end of period	228,265	333,416	535,625
Weighted Average Grant Date Fair Value, Nonvested, beginning of period	$ 34.38	$ 35.10	$ 36.53
Weighted Average Grant Date Fair Value, Granted	$ 58.43	$ 40.98	$ 21.85
Weighted Average Grant Date Fair Value, Vested	$ 35.94	$ 37.48	$ 28.98
Weighted Average Grant Date Fair Value, Forfeited	$ 48.64	$ 39.43	$ 36.03
Weighted Average Grant Date Fair Value, Nonvested, end of period	$ 41.35	$ 34.38	$ 35.10