Comprehensive Income (Details) (USD $) In Thousands	3 Months Ended	6 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Comprehensive Income [Abstract]
Net income	$ 7,051	$ 8,248	$ 9,450	$ 15,393
Unrealized gain (loss) on cash equivalents, marketable securities and restricted investment, net of tax	48	301	137	771
Unrealized gain (loss) on hedge contracts, net of tax	(330)	372	(325)	187
Comprehensive income	$ 6,769	$ 8,921	$ 9,262	$ 16,351

The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the reporting entity. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, but excludes any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.

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- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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- Definition

Change in accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges, net of tax effect. The after tax effect change includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

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Appreciation or loss in value (before reclassification adjustment) of the total of unsold securities during the period being reported on, net of tax. Reclassification adjustments include: (1) the unrealized holding gain (loss), net of tax, at the date of the transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category. Also includes the unrealized gain (loss) at the date of transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category; (2) the unrealized gains (losses) realized upon the sale of securities, after tax; and (3) the unrealized gains (losses) realized upon the write-down of securities, after tax.

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