Equity Compensation (Number Of Restricted Stock Units Granted, Forfeited And Vested) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012
Equity Compensation [Abstract]
# of RSUs, Unvested at beginning of period	314,006
# of RSUs, Granted	257,694
# of RSUs, Forfeited	(5,191)
# of RSUs, Vested	(90,149)
# of RSUs, Unvested at end of period	476,360
Weighted Average Grant Date Fair Value, Unvested at beginning of period	$ 79.44
Weighted Average Grant Date Fair Value, Granted	$ 75.12
Weighted Average Grant Date Fair Value, Forfeited	$ 76.56
Weighted Average Grant Date Fair Value, Vested	$ 81.12
Weighted Average Grant Date Fair Value, Unvested at end of period	$ 76.81