Restructuring And Impairment Costs (Cumulative Restructuring And Impairment Costs) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			3 Months Ended	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010	Dec. 31, 2011 Canadian Operations [Member]	Mar. 31, 2011 Canadian Operations [Member]	Mar. 31, 2011 Fiscal Year 2011 Costs [Member]	Mar. 31, 2011 Fiscal Year 2011 Costs [Member] Closure Of Processing Facility In Canada [Member]	Mar. 31, 2011 Fiscal Year 2011 Costs [Member] Other Restructuring And Cost Reduction Initiatives [Member]	Mar. 31, 2012 Fiscal Year 2012 Costs [Member]	Mar. 31, 2012 Fiscal Year 2012 Costs [Member] Other Restructuring And Cost Reduction Initiatives [Member]	Mar. 31, 2012 Total Costs Cummulative [Member]
Restructuring Cost and Reserve [Line Items]
Employee termination benefits					$ 2,400	$ 11,155	$ 2,412	$ 8,743	$ 8,564	$ 8,564	$ 19,719
Pension curtailment and settlement costs					4,100	4,081	4,081	0	0	0	4,081
Other costs						636	0	636	3,097	3,097	3,733
Impairment costs - Property, plant and equipment				5,600		5,632	5,632	0	0	0	5,632
Restructuring and impairment costs	$ 11,661	$ 21,504	$ 0			$ 21,504	$ 12,125	$ 9,379	$ 11,661	$ 11,661	$ 33,165