Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Mar. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 172,803	$ 184,040
Less allowance for doubtful accounts	2,602	2,838
Accounts receivable, net	170,201	181,202
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	171,274	181,840
Other Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 1,529	$ 2,200