Income Taxes Effective Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Tax provision at statutory rate	35.00%	35.00%	35.00%
Effect of acquisitions/divestitures	24.80%	(3.10%)	0.00%
Effect of foreign operations	(7.70%)	(2.90%)	(1.20%)
State income taxes, net of federal income tax benefit	3.80%	2.30%	3.10%
Benefit of track maintenance credit	0.00%	(6.50%)	(9.30%)
Other, net	(0.30%)	(0.40%)	0.10%
Effective income tax rate	55.60%	24.40%	27.70%