CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 78,710	$ 99,293
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	25,245	25,351
Deferred income taxes	2,927	6,728
Share-based compensation expense related to equity incentive plans	9,986	9,024
Excess tax benefit from share-based compensation	(20)	(385)
Convertible debt derivatives - revaluation and amortization	330	(30)
Amortization of convertible debenture issuance costs	54	55
Amortization of debt discount on convertible debentures	1,975	1,805
Losses on equity method investments	121	61
Unrealized impairment loss on available-for-sale investments	0	945
Changes in operating assets and liabilities:
Increase in accounts receivable	(2,814)	(15,052)
Decrease (increase) in inventories	316	(21,384)
Increase in deferred income on shipments to distributors	2,084	5,554
Increase (decrease) in accounts payable and accrued liabilities	4,766	(17,787)
Change in other assets and liabilities	5,291	(10,873)
Net cash provided by operating activities	128,971	83,305
Cash flows from investing activities:
Purchases of available-for-sale investments	(29,130)	(324,893)
Sales and maturities of available-for-sale investments	139,439	264,485
Business acquisitions	(20,556)	0
Investment in other assets	(1,609)	(976)
Proceeds from sale of assets	50	0
Capital expenditures	(10,304)	(27,219)
Net cash provided by (used in) investing activities	77,890	(88,603)
Cash flows from financing activities:
Payment of cash dividend	(67,749)	(65,900)
Proceeds from sale of common stock	4,961	18,272
Excess tax benefit from share-based compensation	20	385
Net cash used in financing activities	(62,768)	(47,243)
Net increase (decrease) in cash and cash equivalents	144,093	(52,541)
Cash and cash equivalents at beginning of period	635,755	703,924
Cash and cash equivalents at end of period	$ 779,848	$ 651,383