Components of Fixed Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 75,468	$ 63,648
Less - accumulated depreciation	(55,790)	(47,191)
Property, plant and equipment, net, total	19,678	16,457
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Fixed assets, gross	3,337	2,866
Furniture and Fixtures | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Estimated Useful Life	3 years
Furniture and Fixtures | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Estimated Useful Life	7 years
Computer Equipment And Internal Use Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Estimated Useful Life	3 years
Fixed assets, gross	52,170	45,440
Computer Equipment And Internal Use Software | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Estimated Useful Life	3 years
Computer Equipment And Internal Use Software | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Estimated Useful Life	5 years
Demonstration And Spare Part Units
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Estimated Useful Life	2 years
Fixed assets, gross	8,041	6,764
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 11,920	$ 8,578
Leasehold Improvements | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Estimated Useful Life	4 years
Leasehold Improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Estimated Useful Life	12 years