v2.4.0.6

Summary of Significant Accounting Policies (Details 3) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Stock-Based Compensation
Time period of historical volatility of stock used to estimate expected volatility	6 years 6 months 25 days
Stock-based compensation
Share based compensation expense	$ 6.3	$ 7.9
Stock options granted (in shares)	0
Weighted-average assumptions used in the Black-Scholes option-pricing model
Risk-free interest rate (as a percent)	1.08%	1.04%
Expected volatility (as a percent)	46.27%	47.06%
Weighted-average expected life	6 years 6 months 25 days	5 years 9 months 25 days
Forfeiture rate (as a percent)	5.00%	5.00%
Phantom stock unit awards
Stock-based compensation
Share based compensation expense	2.8	1.2
Total compensation cost related to nonvested awards not yet recognized	27.6
Period for recognition of unrecognized compensation cost	3 years 3 months 14 days
Phantom stock unit awards | Minimum
Stock-based compensation
Vesting period	4 years
Phantom stock unit awards | Maximum
Stock-based compensation
Vesting period	5 years
Stock appreciation rights
Stock-based compensation
Share based compensation expense	2.8	1.4
Vesting period	4 years
Total compensation cost related to nonvested awards not yet recognized	$ 12.1
Period for recognition of unrecognized compensation cost	2 years 6 months 4 days

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- Definition

Represents the time period of historical volatility of stock used to estimate expected volatility, in periods.

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The percentage estimated forfeiture rate based on historical experience at the date of the grant.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Net number of share options (or share units) granted during the period.

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