Equity Compensation (Schedule Of Stock Options Granted And Exercised) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Equity Compensation [Abstract]
Shares subject to stock options granted	156,500	159,500
Weighted average grant date fair value per share	$ 31.36	$ 28.90
Shares subject to stock options exercised	104,054	60,530
Intrinsic value of stock options exercised	$ 2,489	$ 911
Proceeds received from stock options exercised	4,668	3,028
Tax benefits realized from stock options exercised	$ 864	$ 351