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Stock-Based Compensation - Weighted Average Fair Value Assumptions (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Weighted Average Fair Value Assumptions [Abstract]
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Risk-free interest rate (as a percent)	1.01%	0.67%	1.80%
Expected volatility (as a percent)	55.20%	58.60%	57.20%
Expected life of option (years)	4 years 8 months 12 days	4 years 9 months 18 days	5 years

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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