CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net income	$ 57,526	$ 178,580
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	76,456	50,528
Deferred income taxes	(9,425)	7,086
Share-based compensation expense related to equity incentive plans	24,593	18,508
Excess tax benefit from share-based compensation	(112)	(402)
Convertible debt derivatives - revaluation and amortization	589	366
Amortization of convertible debenture issuance costs	109	110
Amortization of debt discount on convertible debentures	4,017	3,671
Losses on equity method investments	153	74
Gain on sale of assets	(16)	(48)
Unrealized impairment loss on available-for-sale investments	334	3,009
Changes In Operating Assets And Liabilities
(Increase) decrease in accounts receivable	(116)	38,793
Decrease (increase) in inventories	22,334	(30,074)
Increase in deferred income on shipments to distributors	3,037	4,141
Decrease in accounts payable and accrued liabilities	(27,670)	(50,300)
Change in other assets and liabilities	40,462	14,017
Net cash provided by operating activities	192,271	238,059
Cash flows from investing activities:
Purchases of available-for-sale investments	(443,106)	(665,715)
Sales and maturities of available-for-sale investments	350,593	562,445
Acquisition of SMSC, net of cash acquired	(731,746)	0
Other business acquisitions, net of cash acquired	(20,556)	0
Investment in other assets	(2,204)	(5,146)
Proceeds from sale of assets	66	48
Capital expenditures	(26,212)	(52,449)
Net cash used in investing activities	(873,165)	(160,817)
Cash flows from financing activities:
Proceeds from borrowings on line of credit	600,000	0
Payment of cash dividend	(135,895)	(132,106)
Proceeds from sale of common stock	16,318	25,667
Excess tax benefit from share-based compensation	112	402
Net cash (provided by) used in financing activities	480,535	(106,037)
Effect of foreign exchange rate changes on cash and cash equivalents	1,339	0
Net decrease in cash and cash equivalents	(199,020)	(28,795)
Cash and cash equivalents at beginning of period	635,755	703,924
Cash and cash equivalents at end of period	$ 436,735	$ 675,129