Goodwill and Other Intangibles Estimated Intangible Asset Amortization Expense (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012
Finite-Lived Intangible Assets [Line Items]
2013	$ 6,125
2014	4,686
2015	3,392
2016	3,264
2017	1,913
Later	13,691
Estimated intangible asset amortization expense	33,071
Customer Relationships Intangible [Member]
Finite-Lived Intangible Assets [Line Items]
2013	1,685
2014	1,685
2015	1,685
2016	1,685
2017	1,685
Later	13,691
Estimated intangible asset amortization expense	22,116
Production and Supply Contract Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
2013	1,251
2014	1,251
2015	1,173
2016	1,175
2017	0
Later	0
Estimated intangible asset amortization expense	4,850
Internally Developed Software Intangible [Member]
Finite-Lived Intangible Assets [Line Items]
2013	3,189	[1]
2014	1,750	[1]
2015	534	[1]
2016	404	[1]
2017	228	[1]
Later	0	[1]
Estimated intangible asset amortization expense	$ 6,105	[1]

[1] Estimated amortization expense for the internally developed software is based on costs accumulated as of March 31, 2012. These estimates will change as new costs are incurred and until the software is placed into service in all locations.