Income Taxes Income before income taxes (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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
Provision for income taxes		$ (75,894,000)	$ (107,107,000)	$ (46,296,000)
Provision for income tax as a percentage of income before income taxes		25.20%	29.10%	14.50%
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 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 other than the retroactive benefit from the Short Line Tax Credit				27.40%
Income Tax Expense (Benefit), Continuing Operations, by Jurisdiction [Abstract]
United States income before taxes		$ 236,613,000	276,343,000	$ 211,094,000
Foreign income before taxes		64,318,000	91,519,000	106,498,000
Income before income taxes		300,931,000	$ 367,862,000	317,592,000
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		$ 322,500,000
Tax Year 2012 [Member]
Tax benefit related to the retroactive extension of the United States Short Line Tax Credit				$ 41,000,000