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Stock Based Compensation - Summary of Company Estimated Grant-Date Fair Value of Stock Options Granted Using Black-Scholes Option Valuation Model (Detail)	12 Months Ended
	Dec. 31, 2011
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected dividend yield	0.00%
Expected volatility	47.20%
Risk-free interest rate	2.40%
Risk-free interest rate	2.90%
Expected life	6 years 6 months

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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