CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Mar. 31, 2012
Current assets:
Cash and cash equivalents	$ 204,639	$ 209,335
Short-term investments	150,734	125,177
Accounts receivable, net	108,300	111,771
Inventory, net	58,932	53,713
Deferred tax assets	10,669	11,090
Other current assets	15,854	13,088
Total current assets	549,128	524,174
Long-term investments	29,310	55,347
Property, plant and equipment, net	88,750	76,159
Goodwill and purchased intangibles, net	14,318	14,388
Other assets	2,491	2,402
Total assets	683,997	672,470
Current liabilities:
Accounts payable	29,664	34,126
Accrued liabilities	50,604	51,845
Income taxes payable	4,929	222
Total current liabilities	85,197	86,193
Deferred tax liabilities	2,074	8,673
Long-term income taxes payable	12,714	12,150
Revolving line of credit	42,000	37,000
Other long-term liabilities	1,199	1,210
Total liabilities	143,184	145,226
Commitments and contingencies (Note 6)
Stockholders' equity:
Common stock	746	741
Additional paid-in capital	569,051	557,218
Accumulated other comprehensive income	6,535	6,357
Retained earnings	134,674	115,358
Total stockholders' equity before treasury stock	711,006	679,674
Less: Treasury stock, at cost	(170,193)	(152,430)
Total stockholders' equity	540,813	527,244
Total liabilities and stockholders' equity	$ 683,997	$ 672,470