Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 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			41,200,000
Benefit from/(provision for) income taxes	25,226,000	18,443,000	294,000	30,748,000
Provision for Income Tax as a percentage of income from continuing operations other than 2012 retroactive benefit from the Short Line Tax Credit			27.90%
Effective income tax rate	27.90%	33.60%		34.40%
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