CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities
Net income	$ 130,460	$ 89,909
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	60,375	60,988
Deferred income taxes	(17,509)	(2,319)
Share-based compensation expense related to equity incentive plans	14,112	13,321
Excess tax benefit from share-based compensation	(263)	0
Amortization of debt discount on convertible debentures	11,772	2,365
Amortization of debt issuance costs	958	544
Losses on equity method investments	177	32
Gain on sale of assets	(560)	0
Impairment of intangible assets	0	406
Realized gain on available-for-sale investment	(13,959)	0
Realized gain on equity method investment	(2,225)	0
Amortization of premium on available-for-sale investments	2,396	2,589
Changes In Operating Assets And Liabilities
Increase in accounts receivable	(3,096)	(37,247)
(Increase) decrease in inventories	(23,893)	24,991
Increase (decrease) in deferred income on shipments to distributors	1,401	(1,215)
Increase (decrease) in accounts payable and accrued liabilities	16,157	(4,415)
Change in other assets and liabilities	5,225	15,839
Net cash provided by operating activities	181,528	165,788
Cash flows from investing activities
Purchases of available-for-sale investments	(570,501)	(172,506)
Sales and maturities of available-for-sale investments	433,446	321,203
Sale of equity method investment	2,667	0
Purchase of additional controlling interest in ISSC	(18,051)	0
Acquisition of Supertex, net of cash acquired	0	(375,365)
Investments in other assets	(1,766)	(1,123)
Proceeds from sale of assets	627	0
Capital expenditures	(33,611)	(44,637)
Net cash used in investing activities	(187,189)	(272,428)
Cash flows from financing activities:
Repayments of revolving loan under credit facility	(110,000)	(170,000)
Proceeds from borrowings on revolving loan under credit facility	145,000	504,375
Repayments of long-term borrowings	0	(4,375)
Deferred financing costs	(406)	0
Payment of cash dividends	(72,331)	(71,202)
Proceeds from sale of common stock	3,497	4,125
Tax payments related to shares withheld for vested restricted stock units	(4,464)	(4,968)
Capital lease payments	(166)	(148)
Excess tax benefit from share-based compensation	263	0
Net cash (used in) provided by financing activities	(38,607)	257,807
Net (decrease) increase in cash and cash equivalents	(44,268)	151,167
Cash and cash equivalents at beginning of period	607,815	466,603
Cash and cash equivalents at end of period	$ 563,547	$ 617,770