Effect of Foreign Exchange Forward Contracts on Other Comprehensive Income And Results Of Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	$ 463	[1]	$ (480)	[1]	$ 23	[1]	$ (296)	[1]
Gain (Loss) Reclassified from Accumulated OCI into Income	(79)	[2]	56	[2]	(263)	[2]	231	[2]
Gain (Loss) Recognized in Income (Amount Excluded from Effectiveness Testing)	48	[3]	52	[3]	(92)	[3]	9	[3]
Research And Development | Forward Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative	463	[1]	(480)	[1]	23	[1]	(296)	[1]
Gain (Loss) Reclassified from Accumulated OCI into Income	(89)	[2]	(17)	[2]	(237)	[2]	(3)	[2]
Gain (Loss) Recognized in Income (Amount Excluded from Effectiveness Testing)	47	[3]	21	[3]	(87)	[3]	8	[3]
Sales And Marketing | Forward Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income	10	[2]	73	[2]	(26)	[2]	234	[2]
Gain (Loss) Recognized in Income (Amount Excluded from Effectiveness Testing)	$ 1	[3]	$ 31	[3]	$ (5)	[3]	$ 1	[3]

[1] The amount represents the change in fair value of derivative contracts due to changes in spot rates.

[2] The amount represents reclassification from other comprehensive income to earnings that occurs when the hedged item affects earnings.

[3] The amount represents the change in fair value of derivative contracts due to changes in the difference between the spot price and forward price that is excluded from the assessment of hedge effectiveness and therefore recognized in earnings. No gains or losses were reclassified as a result of discontinuance of cash flow hedges.