Derivative Financial Instruments Foreign Currency Exchange Rate Risk (Details)	12 Months Ended						12 Months Ended					9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 03, 2012 USD ($)	Dec. 01, 2010 USD ($)	Dec. 01, 2010 AUD	Dec. 31, 2012 Foreign Exchange Forward [Member] USD ($)	Dec. 31, 2012 12/3/12 Currency Swap [Member] USD ($)	Dec. 31, 2012 12/1/10 Currency Swap [Member] USD ($)	Dec. 01, 2010 12/1/10 Currency Swap [Member] USD ($)	Dec. 01, 2010 12/1/10 Currency Swap [Member] AUD	Sep. 30, 2012 AUD BBSW Interest Rate [Member] Currency Swap [Member]	Dec. 31, 2012 AUD BBSW Interest Rate [Member] 12/1/10 Currency Swap [Member]	Sep. 30, 2012 Libor Interest Rate [Member] Currency Swap [Member]	Dec. 31, 2012 Libor Interest Rate [Member] 12/1/10 Currency Swap [Member]	Dec. 01, 2010 FreightLink [Member] USD ($)	Dec. 01, 2010 FreightLink [Member] AUD	Dec. 01, 2010 FreightLink [Member] Foreign Exchange Forward [Member] USD ($)
Derivatives [Line Items]
Third-party debt associated with foreign currency debt	$ 220,900,000
Acquisition of assets																320,000,000	331,900,000
Foreign exchange forward contract																		45,000,000
Other income/(expense), net	2,300,000	712,000	(827,000)				(700,000)	300,000	600,000
Intercompany loan				109,600,000	109,600,000	105,000,000				100,600,000	105,000,000
Interest (expense)/income								(300,000)	(4,400,000)
Derivative, description of variable rate basis												Australian dollar BBSW plus 3.25%	Australian dollar BBSW plus 3.125%	LIBOR plus 2.82%	LIBOR plus 2.48%
Derivative settlement payment									$ 9,100,000