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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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Common Stock (Employee Stock Purchase Plan) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Employee Stock Purchase Plan [Member]	May 18, 2012 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Registered shares of common stock					500,000
Percent of common stock fair market value				85.00%
Offering period				3 months
Maximum employee compensation payroll deductions may not exceed				10.00%
Maximum shares employees may purchase in any one offering period				1,000
Share based compensation expense, less than $0.1 million	$ 13.4	$ 7.4	$ 4.7	$ 0.1
Total fair value of the shares purchased under the plan				$ 0.2