Quarterly Financial Data (Details 2) (USD $)	3 Months Ended									12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
After tax gain on sale and impairment of assets		$ 600,000	$ 2,000,000	$ 5,200,000	$ 800,000	$ 1,900,000	$ 400,000	$ 900,000	$ 800,000
Business/corporate development costs, net of tax		(300,000)	(400,000)	(400,000)	(200,000)	(500,000)	(1,400,000)	(300,000)	(100,000)
Insurance recoveries, net of tax		400,000		100,000				700,000
gain on sale of investment net of tax								600,000	200,000
Contingent forward sale contract mark-to-market expense			(50,100,000)							50,106,000	0	0
RailAmerica financing related expenses, net of tax		(9,500,000)
RailAmerica integration costs, net of tax		(6,800,000)
Acquisition related income tax benefits						1,900,000
contract termination expense, net of tax		(800,000)
tax benefit from extension of the short line tax credit	35,000,000					2,200,000	3,200,000	2,500,000	2,200,000
After tax impact of derailment costs						(1,300,000)
RailAmerica [Member]
RailAmerica acquisition related costs, net of tax		(10,900,000)	(3,100,000)	(500,000)
Acquisition/integration costs		$ 3,500,000