Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 233,202	$ 232,719
Less allowance for doubtful accounts	2,709	2,764
Accounts receivable, net	230,493	229,955
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	231,208	230,469
Other Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 1,994	$ 2,250