CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Cash flows from operating activities:
Net income	$ 336,705	$ 418,950	$ 217,005
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	99,424	106,612	90,057
Deferred income taxes	21,954	24,003	22,330
Share-based compensation expense related to equity incentive plans	38,289	36,812	36,778
Excess tax benefit from share-based compensation	(576)	(1,854)	(2,094)
Convertible debt derivatives - revaluation and amortization	204	(185)	230
Amortization of convertible debenture issuance costs	219	219	215
Amortization of debt discount on convertible debentures	7,512	6,847	6,258
Losses (gains) on equity method investments	195	(157)	0
Gain on sale of assets	(411)	(89)	(100)
Unrealized impairment loss on available-for-sale investments	2,158	4,659	4,750
Special (income) charges	(1,000)	0	1,238
Sales of trading securities, net	0	0	86,970
Gain on trading securities	0	0	(7,425)
Changes in operating assets and liabilities:
Decrease (increase) in accounts receivable	11,845	6,341	(49,078)
(Increase) decrease in inventories	(35,240)	(22,068)	15,239
(Decrease) increase in deferred income on shipments to distributors	(31,335)	38,781	15,010
(Decrease) increase in accounts payable and accrued liabilities	(61,455)	(638)	29,583
Change in other assets and liabilities	7,970	(35,572)	(14,919)
Net cash provided by operating activities	396,458	582,661	452,047
Cash flows from investing activities:
Purchases of available-for-sale investments	(1,133,625)	(1,008,056)	(1,576,044)
Sales and maturities of available-for-sale investments	983,500	1,055,286	1,502,127
Purchase of Silicon Storage Technology, Inc, net of cash received	0	(112,707)	0
Investment in Silicon Storage Technology, Inc.	0	0	(58,402)
Investment in other assets	(44,398)	(29,587)	(15,439)
Proceeds from sale of assets	411	31,668	100
Capital expenditures	(62,370)	(124,454)	(47,604)
Net cash used in investing activities	(256,482)	(187,850)	(195,262)
Cash flows from financing activities:
Payment of cash dividend	(266,178)	(256,811)	(249,556)
Proceeds from sale of common stock	57,457	71,940	36,478
Excess tax benefit from share-based compensation	576	1,854	2,094
Net cash used in financing activities	(208,145)	(183,017)	(210,984)
Net (decrease) increase in cash and cash equivalents	(68,169)	211,794	45,801
Cash and cash equivalents at beginning of period	703,924	492,130	446,329
Cash and cash equivalents at end of period	$ 635,755	$ 703,924	$ 492,130