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Summary Of Significant Accounting Policies (Summary Of Weighted-Average Assumptions Used To Value Option Grants) (Details)
12 Months Ended
Dec. 31, 2011
years
Dec. 31, 2010
years
Dec. 31, 2009
years
Summary Of Significant Accounting Policies [Abstract]      
Expected term of options, in years 6.2 7.0 5.7
Expected volatility 41.00% 40.00% 41.00%
Risk-free interest rate 2.674% 2.94% 2.51%
Dividend yield 0.00% 0.00% 0.00%