Business Acquisition (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended			2 Months Ended	3 Months Ended
	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	Dec. 31, 2010 DTE Rail Services, Inc. [Member]	Mar. 31, 2011 DTE Rail Services, Inc. [Member]
Business Acquisition [Line Items]
Revenues	$ 116,579	$ 160,598	$ 181,206	$ 219,066	$ 187,060	$ 130,103	$ 97,583	$ 72,240	$ 677,449	$ 486,986	$ 142,889	$ 4,442
Purchase price adjustment for business acquired													166
Business Acquisition, Cost of Acquired Entity, Cash Paid												23,319
Business Acquisition, Cost of Acquired Entity, Transaction Costs												674
Goodwill, Acquired During Period													76
Goodwill													$ 607