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Stock-Based Compensation (Weighted-Average Assumptions Used to Determine Fair Value of Options Granted) (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Risk-free interest rate	0.52%	0.55%	0.55%	0.65%
Expected life (years)	5 years 5 months	3 years 9 months	4 years 4 months	3 years 9 months
Volatility	48.00%	58.00%	48.00%	58.00%

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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