Accounts Receivable (Details) (USD $) In Thousands	Mar. 31, 2011	Mar. 31, 2010
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 184,040	$ 140,915
Less allowance for doubtful accounts	2,838	3,109
Accounts receivable, net	181,202	137,806
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	181,840	140,340
Other Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 2,200	$ 575