Stock-Based Compensation Valuation Assumptions (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1.6	$ 1.3	$ 4.3	$ 4.8
Options and Ssars [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility			63.60%	63.90%
Expected dividend yield			0.00%	0.00%
Risk-free interest rate			0.70%	2.10%
Expected life of options			5	5
Weighted average fair value of options and SSARs granted			$ 4.75	$ 5.62

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

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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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