Summary of Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Costs and expenses:
Total share-based compensation	$ 964	$ 956
Income tax benefit	(320)	(358)
Decrease in net income	(644)	(598)
Cost of revenue [Member]
Costs and expenses:
Total share-based compensation	76	49
Research and development costs [Member]
Costs and expenses:
Total share-based compensation	59	33
Selling, general and administrative [Member]
Costs and expenses:
Total share-based compensation	$ 829	$ 874