Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 61,192us-gaap_NetIncomeLoss	$ 49,106us-gaap_NetIncomeLoss	$ 40,609us-gaap_NetIncomeLoss
Other comprehensive (loss) income:
Cumulative translation adjustments	(6,311)	1,887	460
Changes in market value of investments:
Changes in unrealized (losses) gains, net of taxes of $0, $0 and $73	(12)	5	109
Total net change in market value of investments	(12)	5	109
Changes in market value of derivatives:
Changes in market value of derivatives, net of (benefit) taxes of ($1,113), $33 and ($146)	(1,937)	62	(258)
Reclassification adjustment for net gains included in net income, net of taxes of $497, $62 and $91	843	147	148
Total net change in market value of derivatives	(1,094)	209	(110)
Other comprehensive (loss) income	(7,417)	2,101	459
Total comprehensive income	$ 53,775us-gaap_ComprehensiveIncomeNetOfTax	$ 51,207us-gaap_ComprehensiveIncomeNetOfTax	$ 41,068us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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