Goodwill and Other Intangibles Goodwill and Intangible Asset Rollforward (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Goodwill and Intangible Assets [Line Items]
Unamortizable Goodwill	$ 2,794	$ 2,794	$ 2,794
Gross balance			58,846
Amortizable Intangibles, Accumulated amortization			(13,855)
Net balance	41,205	44,991
Additions	821	1,308
Impairment of amortizable intangibles	(357)
Amortizable Intangibles, Amortization expense	(5,804)	(5,094)	(5,618)
Net balance	35,865	41,205	44,991
Customer Relationships Intangible [Member]
Goodwill and Intangible Assets [Line Items]
Weighted average remaining useful life (in years)	13
Amortizable Intangibles, Gross carrying amount			33,700
Amortizable Intangibles, Accumulated amortization			(8,214)
Amortizable Intangibles, Net	23,801	25,486
Additions	0	0
Amortizable Intangibles, Amortization expense	(1,685)	(1,685)
Amortizable Intangibles, Net	22,116	23,801
Production and Supply Contract Intangibles [Member]
Goodwill and Intangible Assets [Line Items]
Weighted average remaining useful life (in years)	4
Amortizable Intangibles, Gross carrying amount			7,893
Amortizable Intangibles, Accumulated amortization			(1,452)
Amortizable Intangibles, Net	5,945	6,441
Additions	0	0
Amortizable Intangibles, Amortization expense	(1,095)	(496)
Amortizable Intangibles, Net	4,850	5,945
Internally Developed Software Intangible [Member]
Goodwill and Intangible Assets [Line Items]
Weighted average remaining useful life (in years)	2
Amortizable Intangibles, Gross carrying amount			14,459
Amortizable Intangibles, Accumulated amortization			(4,189)
Amortizable Intangibles, Net	8,665	10,270
Additions	821	1,308
Impairment of amortizable intangibles	(357)
Amortizable Intangibles, Amortization expense	(3,024)	(2,913)
Amortizable Intangibles, Net	$ 6,105	$ 8,665