Income Taxes (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Retroactive tax benefit from extension of the short line tax credit for fiscal year 2012	$ 41,000,000
Income Tax Expense, other than the 2012 retroactive benefit from the Short Line Tax Credit	16,000,000
Income Tax Expense, Continuing Operations	24,932,000	(12,305,000)
Provision for Income Tax as a percentage of income from continuing operations other than 2012 retroactive benefit from the Short Line Tax Credit	27.70%
Effective income tax rate		35.60%
Tax credits percentage of qualified maintenance expenditures to reduce federal income tax	50.00%
Tax credits limitation per mile on maintenance expenditures to reduce federal income tax	$ 3,500