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Stock-Based Compensation Weighted Average Assumptions (Details)
9 Months Ended
Sep. 30, 2011
years
payment
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] 
Expected Dividend Yield0.00%
Risk Free Interest Rate1.85%[1]
Expected Volatility33.10%[2]
Expected Life5.5[3]
[1]The risk-free interest rate for the periods within the contractual term of the options is based on the U.S. Treasury yield curve in effect at the time of the grant.
[2]The expected volatility is a measure of the amount by which a stock price has fluctuated or is expected to fluctuate based primarily on our and our peers' historical data.
[3]The expected life is the period of time, on average, that participants are expected to hold their options before exercise based primarily on our historical data.