Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 290,410	$ 245,323
Less allowance for doubtful accounts	2,937	2,918
Accounts receivable, net	287,473	242,405
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	288,091	243,383
Other Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 2,319	$ 1,940