Stockholders' Equity (Summary Of Anti-Dilutive Options Excluded) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Stockholders' Equity
Options to purchase shares of common stock	818,261	5,466,413	668,791	5,319,890
Weighted-average exercise prices of anti-dilutive options	$ 32.51	$ 24.12	$ 31.85	$ 23.90