Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income tax provision	$ 19,975,000	$ 31,013,000	$ 53,101,000	$ 41,569,000
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	$ 4,200,000		4,200,000
Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit)		$ (1,600,000)
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions				$ 5,500,000
Tax Benefit from United States Short Line Tax Credit, Amount			$ 31,600,000
Effective income tax rate	22.30%	30.00%	24.90%	17.40%
Effective income tax reconciliation excluding short line tax credit and prior period portion of the reserve for uncertain tax positions, percentage				29.10%
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
March 25, 2015 through December 31, 2017
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions		$ 3,700,000