Repurchases Of Common Stock (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Repurchases Of Common Stock [Abstract]
Shares repurchased	687,000	333,000
Total cost of shares repurchased	$ 63,778,000	$ 27,630,000
Average cost per share	$ 92.82	$ 82.85
Shares acquired through employee surrenders	45,181	48,574
Cost of shares acquired through employee surrenders	$ 4,100,000	$ 4,200,000