Derivative Financial Instruments Foreign Currency Exchange Rate Risk (Details)						12 Months Ended				3 Months Ended
	Mar. 31, 2013 USD ($)	Dec. 03, 2012 USD ($)	Dec. 01, 2010 USD ($)	Dec. 01, 2010 FreightLink [Member] USD ($)	Dec. 01, 2010 FreightLink [Member] AUD	Dec. 31, 2012 Cross-Currency Swap 1 [Member] USD ($)	Dec. 01, 2010 Cross-Currency Swap 1 [Member] USD ($)	Dec. 01, 2010 Cross-Currency Swap 1 [Member] AUD	Dec. 01, 2010 Cross-currency swap [Member] AUD	Mar. 31, 2013 AUD BBSW Interest Rate [Member] Cross-Currency Swap 1 [Member]	Mar. 31, 2013 AUD BBSW Interest Rate [Member] Cross-currency swap [Member]	Mar. 31, 2013 LIBOR Interest Rate [Member] Cross-Currency Swap 1 [Member]	Mar. 31, 2013 LIBOR Interest Rate [Member] Cross-currency swap [Member]	Mar. 31, 2013 Not Designated as Hedging Instrument [Member] Cross-currency swap [Member] USD ($)	Mar. 31, 2012 Not Designated as Hedging Instrument [Member] Cross-currency swap [Member] USD ($)
Derivatives [Line Items]
Liability, Reporting Currency Denominated, Value	$ 194,800,000
Business Acquisition, Cost of Acquired Entity, Purchase Price				320,000,000	331,900,000
Notional Amount of Foreign Currency Derivatives		109,600,000	109,600,000				100,600,000	105,000,000	105,000,000
Derivative settlement payment						9,100,000
Derivative, Description of Variable Rate Basis										Australian dollar BBSW plus 3.125%	Australian dollar BBSW plus 3.25%	LIBOR plus 2.48%	LIBOR plus 2.82%
Interest expense, net														$ (814,000)	$ (1,318,000)