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Equity Compensation Plans (Principal Assumptions For SSARs Granted Fair Value) (Details) (USD $)
6 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Equity Compensation Plans    
Weighted average fair value of SSARs granted during the period $ 11.47 $ 10.41
Risk-free interest rate 1.70% 2.20%
Expected volatility 23.20% 29.80%
Expected dividend yield 2.10% 2.20%
Expected life, in years 5 5
Termination rate 0.99% 1.09%
Exercise multiple 1.43 1.38