Property and Equipment and Leases (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Property, Plant and Equipment [Line Items]
Leased Rail Cars	10,315
Leased Locomotives	21
Material payments to Class I carriers under certain lease agreements	$ 0
Equipment
Property, Plant and Equipment [Line Items]
Operating lease expense	19.0	13.1	12.6
Real property
Property, Plant and Equipment [Line Items]
Operating lease expense	$ 4.6	$ 5.0	$ 4.6