Significant Accounting Policies Trade and Other Receivables (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Significant Accounting Policies [Abstract]
Trade receivables	$ 286,992	$ 264,174
Other receivables	16,098	15,730
Allowance for doubtful accounts	3,878	3,732
Charged to costs and expenses	221	3,086	447
Value added tax receivable	$ 12,505	$ 12,282