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Stock-Based Compensation - Stock Option Valuation Assumptions (Details) (Stock Option, USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Weighted average grant-date fair value of options granted	$ 4.08	$ 4.03	$ 6.58
Risk-free interest rate	1.42%	1.50%	1.50%
Expected volatility	68.50%	68.40%	52.30%
Expected term of options	6 years 2 months 12 days	7 years 6 months	5 years 4 months 24 days
Dividend yield	0.00%	0.00%	0.00%

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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