Changes in Operations RailAmerica Purchase Price Allocation (Details) (USD $)	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 28, 2012	Oct. 02, 2012
Business Acquisition [Line Items]
Income from equity investment in RailAmerica, net	$ 0	$ 0	$ 15,557,000
Other comprehensive loss from equity investment in RailAmerica	78,341,000	41,182,000	(9,376,000)
Measurement period adjustment to allocation of fair values to goodwill	295,000	(3,087,000)
Allocation of Fair Value [Abstract]
Goodwill	628,815,000	630,462,000	634,953,000
RailAmerica [Member]
Business Acquisition [Line Items]
Reduction in net cash paid for acquisition due to change in cash and cash equivalents				(21,800,000)
Measurement period adjustment to the allocation of fair values to property and equipment		10,700,000
Measurement period adjustment to the allocation of fair values to intangible assets		(29,900,000)
Measurement period adjustment to the allocation of fair values to deferred income tax liabilities, net		(16,000,000)
Measurement period adjustment to the allocation of fair values to noncontrolling interest		(5,000,000)
Measurement period adjustment to the allocation of fair values to all other assets, net		1,300,000
Measurement period adjustment to allocation of fair values to goodwill		(3,100,000)
Additional depreciation and amortization expense as a result of the measurement period adjustment to the allocation of fair values		4,000,000
Allocation of Fair Value [Abstract]
Cash and cash equivalents				107,922,000	86,102,000
Accounts receivable				91,424,000	104,839,000
Materials and supplies				7,325,000	6,406,000
Prepaid expenses and other				14,815,000	15,146,000
Deferred income tax assets				49,074,000	49,074,000
Property and equipment				1,588,612,000	1,579,321,000
Goodwill				474,115,000	474,115,000
Intangible assets				446,327,000	451,100,000
Other assets				116,000	116,000
Total assets				2,779,730,000	2,766,219,000
Accounts payable and accrued expenses				135,117,000	143,790,000
Long-term debt				12,010,000	12,158,000
Deferred income tax liabilities, net				551,856,000	542,210,000
Other long-term liabilities				19,618,000	20,754,000
Noncontrolling interest				5,525,000	5,525,000
Net assets				2,055,604,000	2,041,782,000
RailAmerica [Member] | Final allocation of fair values [Member]
Allocation of Fair Value [Abstract]
Cash and cash equivalents				107,922,000
Accounts receivable				90,659,000
Materials and supplies				7,325,000
Prepaid expenses and other				15,801,000
Deferred income tax assets				56,998,000
Property and equipment				1,599,282,000
Goodwill				471,028,000
Intangible assets				416,427,000
Other assets				116,000
Total assets				2,765,558,000
Accounts payable and accrued expenses				140,160,000
Long-term debt				12,010,000
Deferred income tax liabilities, net				535,864,000
Other long-term liabilities				21,439,000
Noncontrolling interest				481,000
Net assets				2,055,604,000
RailAmerica [Member]
Business Acquisition [Line Items]
Income from equity investment in RailAmerica, net				15,600,000
Other comprehensive loss from equity investment in RailAmerica				$ (2,000,000)