Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Mar. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 177,274	$ 172,803
Less allowance for doubtful accounts	2,589	2,602
Accounts receivable, net	174,685	170,201
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	175,606	171,274
Other Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 1,668	$ 1,529