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Stockholders' Equity - Schedule of Black-Scholes Assumptions Used for Stock Options and Stock Appreciations Rights (Detail) (Stock Options [Member])	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	0.93%	0.99%
Risk-free interest rate, maximum	0.94%	1.18%
Estimated term (in years)	5 years 2 months 27 days	5 years 5 months 23 days
Estimated volatility	68.00%	73.00%
Estimated dividend yield

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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