Income Taxes Components of Net Deferred Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
DEFERRED INCOME TAX ASSETS, net	$ 2,671	$ 2,270
DEFERRED INCOME TAX LIABILITIES, net	1,162,221	983,136
Deferred tax assets [Abstract]
Net operating loss carryforwards	23,168	20,810
Accruals and reserves not deducted for tax purposes until paid	15,131	14,896
Stock-based compensation	10,089	9,253
Deferred revenue	6,311	5,736
Deferred compensation	3,891	3,454
Nonshareholder contributions	1,978	2,150
Interest rate swaps	0	4,223
Alternative minimum tax credit carryforward	1,592	1,592
Pension and postretirement benefits	18,693	15,411
Other	2,072	752
Total deferred tax assets	299,979	315,688
Valuation allowance	(24,075)	(19,315)	$ (14,793)
Deferred tax liabilities [Abstract]
Interest rate swaps	(4,579)	0
Property and equipment basis difference	(1,012,109)	(967,998)
Intangible assets basis difference	(418,398)	(302,903)
Other	(368)	(6,338)
Net deferred tax liabilities	(1,159,550)	(980,866)
Track maintenance credit [Member]
Deferred tax assets [Abstract]
Track maintenance credit carryforward	$ 217,054	237,411
Accounting Standards Update 2015-17 [Member]
Deferred Tax Assets, Net, Current		(69,200)
DEFERRED INCOME TAX ASSETS, net		200
DEFERRED INCOME TAX LIABILITIES, net		$ (69,000)