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

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

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.

+ References

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

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- Definition

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.

+ References

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- Definition

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.

+ References

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- Definition

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.

+ References

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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- Definition

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.

+ References

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- Definition

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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- Definition

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

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- Definition

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

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Summary of Significant Accounting Policies (Details 3) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 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	$ 5.4	$ 7.4	$ 11.7	$ 15.3
Stock options granted (in shares)			0
Restricted stock granted (in shares)			256,500
Weighted-average assumptions used in the Black-Scholes option-pricing model
Risk-free interest rate (as a percent)			1.08%	0.84%
Expected volatility (as a percent)			46.27%	45.78%
Weighted-average expected life			6 years 6 months 25 days	6 years 7 months 20 days
Forfeiture rate (as a percent)			5.00%	5.00%
Phantom stock unit awards
Stock-based compensation
Share based compensation expense	2.2	1.3	5.0	2.5
Total compensation cost related to nonvested awards not yet recognized	27.6		27.6
Period for recognition of unrecognized compensation cost			3 years 29 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	0.9	1.1	3.7	2.5
Vesting period			4 years
Total compensation cost related to nonvested awards not yet recognized	$ 11.2		$ 11.2
Period for recognition of unrecognized compensation cost			2 years 3 months 11 days