CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $)	9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income	$ 67,699,000	$ 256,069,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	140,468,000	75,170,000
Deferred income taxes	(9,981,000)	7,185,000
Share-based compensation expense related to equity incentive plans	38,713,000	28,470,000
Excess tax benefit from share-based compensation	(154,000)	(441,000)
Convertible debt derivatives - revaluation and amortization	253,000	427,000
Amortization of convertible debenture issuance costs	164,000	165,000
Amortization of debt discount on convertible debentures	6,106,000	5,580,000
Losses on equity method investments	382,000	60,000
Gain on sale of assets	(256,000)	(212,000)
Loss on write-down of fixed assets	400,000	0
Unrealized impairment loss on available-for-sale investments	412,000	3,213,000
Special income	0	(1,000,000)
Changes In Operating Assets And Liabilities
Decrease in accounts receivable	52,839,000	31,925,000
Decrease (increase) in inventories	47,146,000	(36,297,000)
Increase (decrease) in deferred income on shipments to distributors	2,526,000	(24,258,000)
Decrease in accounts payable and accrued liabilities	(58,539,000)	(67,198,000)
Change in other assets and liabilities	33,000,000	15,140,000
Net cash provided by operating activities	321,178,000	293,998,000
Cash flows from investing activities:
Purchases of available-for-sale investments	(646,424,000)	(962,119,000)
Sales and maturities of available-for-sale investments	517,707,000	793,238,000
Acquisition of SMSC, net of cash acquired	(731,746,000)	0
Other business acquisitions, net of cash acquired	(20,556,000)	0
Investment in other assets	(4,018,000)	(6,878,000)
Proceeds from sale of assets	306,000	212,000
Capital expenditures	(36,076,000)	(58,582,000)
Net cash used in investing activities	(920,807,000)	(234,129,000)
Cash flows from financing activities:
Proceeds from borrowings on line of credit	610,000,000	0
Payment of cash dividend	(204,592,000)	(198,919,000)
Proceeds from sale of common stock	22,619,000	40,410,000
Excess tax benefit from share-based compensation	154,000	441,000
Net cash provided by (used in) financing activities	428,181,000	(158,068,000)
Effect of foreign exchange rate changes on cash and cash equivalents	986,000	0
Net decrease in cash and cash equivalents	(170,462,000)	(98,199,000)
Cash and cash equivalents at beginning of period	635,755,000	703,924,000
Cash and cash equivalents at end of period	$ 465,293,000	$ 605,725,000