CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Mar. 31, 2012
Current assets:
Cash and cash equivalents	$ 196,656	$ 209,335
Short-term investments	132,245	125,177
Accounts receivable, net	112,677	111,771
Inventory, net	66,905	53,713
Deferred tax assets	11,208	11,090
Other current assets	13,301	13,088
Total current assets	532,992	524,174
Long-term investments	79,619	55,347
Property, plant, and equipment, net	93,552	76,159
Goodwill and purchased intangibles, net	16,773	14,388
Other assets	2,521	2,402
Total assets	725,457	672,470
Current liabilities:
Accounts payable	36,012	34,126
Accrued liabilities	58,270	52,067
Total current liabilities	94,282	86,193
Deferred tax liabilities	2,158	8,673
Long-term income taxes payable	11,636	12,150
Revolving line of credit	20,000	37,000
Other long-term liabilities	1,008	1,210
Total liabilities	129,084	145,226
Commitments and contingencies (Note 6)
Stockholders' equity:
Common stock	750	741
Additional paid-in capital	588,148	557,218
Accumulated other comprehensive income	3,524	6,357
Retained earnings	180,295	115,358
Total stockholders' equity before treasury stock	772,717	679,674
Less: Treasury stock, at cost	(176,344)	(152,430)
Total stockholders' equity	596,373	527,244
Total liabilities and stockholders' equity	$ 725,457	$ 672,470