Edith River Derailment (Details)	12 Months Ended			3 Months Ended					12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Jun. 30, 2012 Edith River Derailment [Member] USD ($)	Jun. 30, 2012 Edith River Derailment [Member] AUD	Mar. 31, 2012 Edith River Derailment [Member] USD ($)	Dec. 31, 2011 Edith River Derailment [Member] USD ($)	Dec. 31, 2011 Edith River Derailment [Member] AUD	Dec. 31, 2012 Edith River Derailment [Member] USD ($)	Dec. 31, 2012 Edith River Derailment [Member] AUD	Dec. 31, 2012 Accounts receivable insurance claims [Member] USD ($)	Dec. 31, 2011 Accounts receivable insurance claims [Member] USD ($)	Dec. 31, 2012 Accounts receivable insurance claims [Member] Edith River Derailment [Member] USD ($)	Dec. 31, 2012 Accounts receivable insurance claims [Member] Edith River Derailment [Member] AUD	Dec. 31, 2011 Accounts receivable insurance claims [Member] Edith River Derailment [Member] USD ($)	Dec. 31, 2011 Accounts receivable insurance claims [Member] Edith River Derailment [Member] AUD
Business Interruption Loss [Line Items]
Lost Revenues During The Period Due To A Specified Event						$ 7,000,000
Gain on Business Interruption Insurance Recovery				4,800,000	4,800,000
Estimated accrued repair costs							15,300,000	15,000,000	13,300,000	12,800,000
Accounts Receivable, Gross, Current	265,642,000	168,575,000									26,443,000	17,336,000	4,900,000	4,700,000	14,300,000	14,000,000
Payment of derailment costs									27,300,000	26,300,000
Proceeds from Insurance Settlement, Operating Activities	$ 21,479,000	$ 646,000	$ 0						$ 20,900,000	22,100,000