Stock-Based Compensation Compensation Costs from Equity Awards (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount		$ 7.9	$ 7.7	$ 7.1
compensation costs from accelerated of RailAmerica equity awards	4.1
Compensation costs related to non-vested awards not yet recognized	20.7	20.7
Weighted average period over which non-vested awards will be recongized		1 year 8 months 3 days
Income tax benefit recognized		4.5	2.6	2.5
Total income tax benefit realized from exercise of equity awards		$ 10.9	$ 5.0	$ 4.3

compensation costs from accelerated of RailAmerica equity awards

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-Number 123R

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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.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

+ References

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- Definition

Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

+ References

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-Name Accounting Standards Codification

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