Federal Statutory Income Tax Rate (Detail)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Schedule of Effective Tax Rate Reconciliation [Line Items]
Statutory U.S. federal tax rate	35.00%	35.00%	35.00%
State taxes, net of federal tax effect	3.60%	3.20%	3.00%
Research and development tax credits	(2.10%)	(2.10%)	(2.10%)
Tax rate differential of foreign operations	0.70%	0.10%	(0.20%)
Domestic production activities deduction	(2.90%)	(2.40%)	(3.00%)
Transaction costs	0.70%	1.50%	0.00%
Other	1.30%	1.00%	1.10%
Total effective income tax rate	36.30%	36.30%	33.80%