Income Taxes Income before income taxes (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Tax credits percentage of qualified maintenance expenditures to reduce federal income tax		50.00%
Tax credit limitation per mile on maintenance expenditures to reduce federal income tax		$ 3,500
Income tax expense		107,107,000	46,296,000	46,402,000
Provision for income tax as a percentage of income before income taxes and income from equity investment		29.10%	14.50%	55.60%
Tax benefit from retroactive change in tax accounting method related to acquired companies	3,900,000	3,900,000
Provision for income taxes other than the 2012 Retroactive Benefit from the Short Line Tax Credit, Continuing Operations			87,200,000
Provision for income tax as a percentage of income before income taxes and income from equity investment other than the 2012 retroactive benefit from the Short Line Tax Credit			27.40%
Income Tax Nondeductible Expense, Contingent Forward Sale Contract Mark-to-Market Expense, Amount				50,100,000
Provision for income tax as a percentage of income before income taxes and income from equity investment other than non-deductible mark-to-market expense on contingent forward sale contract.				34.80%
Income Tax Expense (Benefit), Continuing Operations, by Jurisdiction [Abstract]
United States income before taxes and income from equity investment		276,594,000	211,889,000	5,598,000
Foreign income before taxes and income from equity investment		91,519,000	106,498,000	77,680,000
Income before income taxes and income from equity investment		368,113,000	318,387,000	83,278,000
Provision for United States income taxes applicable to undistributed foreign earnings		0
Determination of Deferred Tax Liability is Not Practicable, Undistributed Earnings of Foreign Subsidiaries		the amount of the tax and credits is not practicable to determine
Undistributed foreign earnings		305,200,000
Tax Year 2012 [Member]
Tax benefit related to the retroactive extension of the United States Short Line Tax Credit			$ 41,000,000