Stockholders' Equity (Summary Of Stock Options Granted) (Details) (USD $)	1 Months Ended		3 Months Ended
	Apr. 20, 2012	Apr. 17, 2012	Mar. 31, 2012 April 19, 2011 [Member]	Mar. 31, 2012 April 20, 2010 [Member]	Mar. 31, 2012 April 21, 2009 [Member]	Mar. 31, 2012 April 15, 2008 [Member]	Mar. 31, 2012 April 17, 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	1,200,000		410,000	530,000	790,000	550,000	4,380,000
Option exercise (strike) price		$ 54.00	$ 35.00	$ 30.00	$ 27.00	$ 27.00	$ 22.50
Closing stock price on date of grant		$ 49.01	$ 31.78	$ 27.13	$ 17.61	$ 24.35	$ 20.15
Options outstanding			400,000	390,000	590,000	350,000	2,555,050
Options vested			0	0	0	0	1,040,050