Derivative Financial Instruments (Details)	12 Months Ended									12 Months Ended
	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 01, 2010 USD ($)	Dec. 01, 2010 AUD	Oct. 02, 2008 USD ($)	Dec. 31, 2011 Cross-currency swap agreement [Member] USD ($)	Dec. 01, 2010 FreightLink [Member] USD ($)	Dec. 01, 2010 FreightLink [Member] AUD	Dec. 31, 2011 AUD BBSW Interest Rate [Member]	Dec. 31, 2011 Libor Interest Rate [Member]	Dec. 31, 2011 Cross-currency swap agreement [Member] USD ($)	Dec. 31, 2010 Cross-currency swap agreement [Member] USD ($)	Dec. 01, 2010 Foreign exchange forward contracts [Member] FreightLink [Member] USD ($)
Derivatives [Line Items]
Notional amount of interest rate swap						$ 120,000,000
Fixed rate on notional amount of interest rate swap						3.88%
Gain (loss) reclassified from accumulated OCI into earnings	0
Third-party debt associated with foreign currency debt	181,800,000
Acquisition of assets								320,000,000	331,900,000
Intercompany loan				100,600,000	105,000,000
Derivative, description of variable rate basis										Australian dollar BBSW plus 3.125%	LIBOR plus 2.48%
Interest (expense)/income												(5,935,000)	(449,000)
Other income/(expense), net	712,000	(827,000)	2,115,000									246,000	(975,000)
Derivative liability, net							7,200,000
Foreign exchange forward contract														$ 45,000,000