Microchip Technology (MCHP) 10-Q 7 Feb 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	9 Months Ended
	Dec. 31, 2013	Jan. 31, 2014
DEI Information [Abstract]	'	'
Entity Registrant Name	'MICROCHIP TECHNOLOGY INC	'
Entity Central Index Key	'0000827054	'
Current Fiscal Year End Date	'--03-31	'
Entity Filer Category	'Large Accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	31-Dec-13	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	199,134,437

CONDENSED_CONSOLIDATED_BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (USD $)	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
ASSETS	'	'
Cash and cash equivalents	$375,100	$528,334
Short-term investments	932,302	1,050,263
Accounts receivable, net	224,273	229,955
Inventories	274,629	242,334
Prepaid expenses	29,441	37,439
Deferred tax assets	72,142	80,687
Other current assets	61,141	67,358
Total current assets	1,969,028	2,236,370
Property, plant and equipment, net	520,565	514,544
Long-term investments	723,925	257,450
Goodwill	275,967	271,348
Intangible assets, net	466,278	530,136
Other assets	47,345	41,557
Total assets	4,003,108	3,851,405
LIABILITIES AND STOCKHOLDERS' EQUITY	'	'
Accounts payable	62,750	75,551
Accrued liabilities	96,176	127,108
Short-term borrowings	14,159	0
Deferred income on shipments to distributors	143,315	138,952
Total current liabilities	316,400	341,611
Junior convertible debentures	369,618	363,385
Long-term line of credit	300,000	620,000
Long-term borrowings, net	335,694	0
Long-term income tax payable	179,246	182,723
Deferred tax liability	388,620	388,250
Other long-term liabilities	38,422	21,966
Stockholders' equity:	'	'
Preferred stock, $0.001 par value; authorized 5,000,000 shares; no shares issued or outstanding	0	0
Common stock, $0.001 par value; authorized 450,000,000 shares; 218,789,994 shares issued and 199,117,558 shares outstanding at December 31, 2013; 218,789,994 shares issued and 196,472,856 shares outstanding at March 31, 2013	199	196
Additional paid-in capital	1,254,764	1,255,627
Common stock held in treasury: 19,672,436 shares at December 31, 2013; 22,317,138 shares at March 31, 2013	-603,672	-682,220
Accumulated other comprehensive (loss) income	-2,579	6,935
Retained earnings	1,426,396	1,352,932
Total stockholders' equity	2,075,108	1,933,470
Total liabilities and stockholders' equity	$4,003,108	$3,851,405

CONDENSED_CONSOLIDATED_BALANCE1

CONDENSED CONSOLIDATED BALANCE SHEETS CONDENSED CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) (USD $)	Dec. 31, 2013	Mar. 31, 2013
Preferred Stock, Par or Stated Value Per Share	$0.00	$0.00
Preferred Stock, Shares Authorized	5,000,000	5,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common Stock, Par or Stated Value Per Share	$0.00	$0.00
Common Stock, Shares Authorized	450,000,000	450,000,000
Common Stock, Shares, Issued	218,789,994	218,789,994
Common Stock, Shares, Outstanding	199,117,558	196,472,856
Treasury Stock, Shares	19,672,436	22,317,138

CONDENSED_CONSOLIDATED_STATEME

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (unaudited) (USD $)	3 Months Ended				9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2013		Dec. 31, 2012
Income Statement	'		'		'		'
Net sales	$482,372		$416,047		$1,437,833		$1,151,479
Cost of sales	199,652	[1]	215,619	[1]	599,676	[1]	552,059	[1]
Gross profit	282,720		200,428		838,157		599,420
Operating expenses:	'		'		'		'
Research and development	76,341	[1]	71,377	[1]	227,680	[1]	184,285	[1]
Selling, general and administrative	66,856	[1]	69,368	[1]	201,934	[1]	196,727	[1]
Amortization of acquired intangible assets	21,804		39,711		73,225		71,615
Special charges	801		2,559		2,491		24,953
Total operating expenses	165,802		183,015		505,330		477,580
Operating income	116,918		17,413		332,827		121,840
Losses on equity method investments	150		-229		-211		-382
Other income (expense):	'		'		'		'
Interest income	4,241		3,813		12,176		11,889
Interest expense	-12,545		-11,077		-36,755		-30,983
Other income (expense), net	3,824		-228		6,093		311
Income before income taxes	112,588		9,692		314,130		102,675
Income tax provision (benefit)	7,187		-481		30,344		34,976
Net income	105,401		10,173		283,786		67,699
Basic net income per common share	$0.53		$0.05		$1.43		$0.35
Diluted net income per common share	$0.48		$0.05		$1.31		$0.33
Dividends declared per common share	$0.35		$0.35		$1.06		$1.05
Basic common shares outstanding	198,759		194,958		197,845		194,157
Diluted common shares outstanding	219,089		204,405		215,943		204,553
Allocated Share-based Compensation Expense	$12,209		$11,365		$36,874		$37,163
[1]	Includes share-based compensation expense as follows:Cost of sales 1,841 1,834 5,674 5,758 Research and development 6,141 6,172 18,762 16,562 Selling, general and administrative 5,737 6,114 16,939 22,339

CONDENSED_CONSOLIDATED_STATEME1

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (PARENTHETICAL) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2013		Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	$12,209		$11,365		$36,874		$37,163
Cost of Sales [Member]	'		'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	1,841	[1]	1,834	[1]	5,674	[1]	5,758	[1]
Research and Development Expense [Member]	'		'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	6,141		6,172		18,762		16,562
Selling General And Administrative Member	'		'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	$5,737		$6,114		$16,939		$22,339
[1]	During the three and nine months ended DecemberB 31, 2013, $1.9 million and $5.7 million, respectively, of share-based compensation expense was capitalized to inventory and $1.8 million and $5.7 million, respectively, of previously capitalized share-based compensation expenses in inventory was sold. During the three and nine months ended DecemberB 31, 2012, $1.8 million and $5.3 million, respectively, of share-based compensation expense was capitalized to inventory and $1.8 million and $5.8 million, respectively, of previously capitalized share-based compensation expense in inventory was sold.

CONDENSED_CONSOLIDATED_STATEME2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Net income	$105,401	$10,173	$283,786	$67,699
Unrealized holding gain (losses), net of tax effect of $0, $83, $497 and $119, respectively	59	-200	-8,011	2,418
Reclassification of realized transactions, net of tax effect of $0, $0, $776, and $51, respectively	-113	-14	-1,503	-184
Change in net foreign currency translation adjustment	0	299	0	1,439
Other comprehensive (loss) income, net of taxes	-54	85	-9,514	3,673
Total comprehensive income	$105,347	$10,258	$274,272	$71,372

CONDENSED_CONSOLIDATED_STATEME3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (PARENTHETICAL) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Statement of Other Comprehensive Income [Abstract]	'	'	'	'
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax, Portion Attributable to Parent	$0	$83	$497	$119

CONDENSED_CONSOLIDATED_STATEME4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities	'	'
Net income	$283,786	$67,699
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	143,704	140,468
Deferred income taxes	24,190	-9,981
Share-based compensation expense related to equity incentive plans	41,375	38,713
Excess tax benefit from share-based compensation	0	-154
Convertible debt derivatives - revaluation and amortization	-449	253
Amortization of debt discount on convertible debentures	6,682	6,106
Amortization of debt issuance costs	1,416	164
Losses on equity method investments	211	382
Gain on sale of assets	0	-256
Loss on write-down of fixed assets	0	400
Impairment of intangible assets	350	0
Amortization of premium on available-for-sale investments	8,067	10,304
Unrealized impairment loss on available-for-sale investments	0	412
Special income, net	-999	0
Gain on shares of acquired company	-2,438	0
Changes In Operating Assets And Liabilities	'	'
Decrease in accounts receivable	5,624	52,839
(Increase) decrease in inventories	-30,588	47,146
Increase in deferred income on shipments to distributors	4,363	2,526
Decrease in accounts payable and accrued liabilities	-21,870	-58,539
Change in other assets and liabilities	9,799	33,000
Net cash provided by operating activities	473,223	331,482
Cash flows from investing activities	'	'
Purchases of available-for-sale investments	-950,560	-656,728
Sales and maturities of available-for-sale investments	584,186	517,707
Acquisition of SMSC, net of cash acquired	0	-731,746
Other business acquisitions, net of cash acquired	-11,187	-20,556
Investments in other assets	-7,462	-4,018
Proceeds from sale of assets	16,200	306
Capital expenditures	-79,536	-36,076
Net cash used in investing activities	-448,359	-931,111
Cash flows from financing activities:	'	'
Repayments of revolving loan under previous credit facility	-650,000	-130,000
Repayments of revolving loan under new credit facility	-153,500	0
Proceeds from borrowings on revolving loan under previous credit facility	30,000	740,000
Proceeds from borrowings on revolving loan under new credit facility	453,500	0
Proceeds from issuance of long-term borrowings	350,000	0
Deferred financing costs	-7,515	0
Payment of cash dividends	-210,322	-204,592
Proceeds from sale of common stock	24,752	22,619
Contingent consideration payment	-14,700	0
Capital lease payments	-313	0
Excess tax benefit from share-based compensation	0	154
Net cash (used in) provided by financing activities	-178,098	428,181
Effect of foreign exchange rate changes on cash and cash equivalents	0	986
Net decrease in cash and cash equivalents	-153,234	-170,462
Cash and cash equivalents at beginning of period	528,334	635,755
Cash and cash equivalents at end of period	$375,100	$465,293

Basis_of_Presentation_Notes

Basis of Presentation (Notes)	9 Months Ended
	Dec. 31, 2013
Basis of Presentation [Abstract]	'
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	'
	Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements include the accounts of Microchip Technology Incorporated and its wholly-owned subsidiaries (the Company).  All intercompany balances and transactions have been eliminated in consolidation.  The Company owns 100% of the outstanding stock in all of its subsidiaries.
	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America, pursuant to the rules and regulations of the Securities and Exchange Commission (the SEC).  The information furnished herein reflects all adjustments which are, in the opinion of management, of a normal recurring nature and necessary for a fair statement of the results for the interim periods reported. Certain information and footnote disclosures normally included in audited consolidated financial statements have been condensed or omitted pursuant to such SEC rules and regulations.  It is suggested that these condensed consolidated financial statements be read in conjunction with the audited consolidated financial statements and the notes thereto included in the Company's Annual Report on Form 10-K for the fiscal year ended March 31, 2013.  The results of operations for the nine months ended December 31, 2013 are not necessarily indicative of the results that may be expected for the fiscal year ending March 31, 2014 or for any other period.

Reclassification_of_Prior_Peri

Reclassification of Prior Periods (Notes)	9 Months Ended
	Dec. 31, 2013
Accounting Changes and Error Corrections [Abstract]	'
Reclassification of Prior Periods	'
	Reclassification of Prior Periods
	In the quarter ended December 31, 2013, the Company identified an error to the presentation on the condensed consolidated statements of cash flows of the amortization of premium of available-for-sale investments. The Company previously included the amortization of the premium as an investing activity. This amortization is a non-cash expense that should be recorded in the adjustments to reconcile net income to net cash provided by operating activities. The Company has corrected this error in the current period, and has conformed previous periods to the current presentation. Based on the Company's evaluation of relevant quantitative and qualitative factors, it determined that the classification errors are immaterial to the prior period financial statements and the Company plans to correct the comparative presentation of the prior periods in future filings. The effect on net cash provided by operating activities and net cash used in investing activities for the previous period covered by this report are shown below (amounts in thousands):
		Nine Months Ended
		31-Dec-12
		As reported			Adjustment			As adjusted
	Cash flows from operating activities
	Amortization of premium on available-for-sale investments	$	—		$	10,304		$	10,304
	Net cash provided by operating activities	321,178			10,304			331,482
	Cash flows from investing activities
	Purchases of available-for-sale investments	(646,424		)	(10,304		)	(656,728		)
	Net cash used in investing activities	(920,807		)	(10,304		)	(931,111		)
	This correction does not affect the Company's condensed consolidated statements of income, condensed consolidated balance sheets or condensed consolidated statements of comprehensive income for any periods.

Business_Acquisitions_Notes

Business Acquisitions (Notes)	9 Months Ended
	Dec. 31, 2013
Business Acquisition [Line Items]	'
Business Combination Disclosure [Text Block]	'
	Business Acquisitions
	On November 21, 2013, the Company completed an acquisition which was accounted for under the acquisition method of accounting. The Company had a prior 18.3% ownership interest in the acquired company accounted for as a cost method investment and recognized an approximate $2.4 million gain to write that ownership interest up to fair value in the three and nine-month periods ended December 31, 2013. The total consideration paid for the remaining 81.7% equity of the business, net of cash acquired, was $9.0 million. The purchase price of the acquisition resulted in purchased intangible assets of $4.1 million and goodwill of approximately $6.4 million. The purchased intangible assets are being amortized over a weighted average period of approximately 8 years.
	On August 2, 2012, the Company acquired Standard Microsystems Corporation (SMSC), a publicly traded company based in Hauppauge, New York. The acquisition was accounted for under the acquisition method of accounting. The Company retained an independent third-party appraiser to assist management in its valuation. The table below represents the allocation of the purchase price, including adjustments to the purchase price allocation from the previously reported figures at March 31, 2013, to the net assets acquired based on their estimated fair values as of August 2, 2012. The purchase price allocation was finalized as of August 2, 2013. All adjustments shown in the table below were recorded during the three months ended June 30, 2013 (amounts in thousands):
	Assets acquired	Previously Reported			Adjustments			31-Dec-13
		31-Mar-13
	Cash and cash equivalents	$	180,925		$	—		$	180,925
	Accounts receivable, net	58,441			—			58,441
	Inventories	86,244			—			86,244
	Prepaid expenses	5,617			—			5,617
	Deferred tax assets	15,843			—			15,843
	Other current assets	17,578			—			17,578
	Property, plant and equipment, net	35,608			—			35,608
	Long-term investments	24,275			—			24,275
	Goodwill	169,065			(3,473		)	165,592
	Intangible assets, net	10,214			—			10,214
	Purchased intangible assets	517,800			—			517,800
	Other assets	3,835			—			3,835
	Total assets acquired	1,125,445			(3,473		)	1,121,972
	Liabilities assumed
	Accounts payable	(28,035		)	—			(28,035		)
	Accrued liabilities	(62,038		)	(209		)	(62,247		)
	Deferred income on shipments to distributors	(11,376		)	—			(11,376		)
	Long-term income tax payable	(72,781		)	—			(72,781		)
	Deferred tax liability	(21,079		)	4,397			(16,682		)
	Other liabilities	(10,535		)	(715		)	(11,250		)
	Total liabilities assumed	(205,844		)	3,473			(202,371		)
	Purchase price allocated	$	919,601		$	—		$	919,601

Recently_Issued_Accounting_Pro

Recently Issued Accounting Pronouncements (Notes)	9 Months Ended
	Dec. 31, 2013
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
Description of New Accounting Pronouncements Not yet Adopted [Text Block]	'
	Recently Issued Accounting Pronouncements
	In the first quarter of fiscal 2014, the Company adopted the provisions of Accounting Standard Update 2013-02 Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income, which required the disclosure of amounts reclassified out of accumulated other comprehensive income (AOCI) to net income. The adoption of this provision did not have a material impact on the Company's consolidated financial statements and related disclosures (See Note 19).

Special_Charges_Notes

Special Charges (Notes)	9 Months Ended
	Dec. 31, 2013
Notes to Financial Statements [Abstract]	'
Special charges	'
	Special Charges
	During the three and nine months ended December 31, 2013, the Company incurred severance related, office closing and other costs associated with its acquisition activity of $0.8 million and $2.5 million, respectively.
	During the three and nine months ended December 31, 2012, the Company incurred approximately $2.6 million and $13.4 million, respectively, of severance related, office closing, and other costs associated with the acquisition of SMSC. Also, during the nine months ended December 31, 2012, the Company incurred legal settlement costs of approximately $11.5 million for certain legal matters related to Silicon Storage Technology, Inc. (which the Company acquired in April 2010) in excess of previously accrued amounts.

Segment_Information_Notes

Segment Information (Notes)	9 Months Ended
	Dec. 31, 2013
Segment Reporting [Abstract]	'
Segment Reporting Disclosure [Text Block]	'
	Segment Information
	The Company's reportable segments are semiconductor products and technology licensing.  The Company does not allocate operating expenses, interest income, interest expense, other income or expense, or provision for or benefit from income taxes to these segments for internal reporting purposes, as the Company does not believe that allocating these expenses is beneficial in evaluating segment performance.  Additionally, the Company does not allocate assets to segments for internal reporting purposes as it does not manage its segments by such metrics.
	The following table represents net sales and gross profit for each segment for the three and nine months ended December 31, 2013 (amounts in thousands):
		Three Months Ended				Nine Months Ended
		December 31, 2013				December 31, 2013
		Net Sales		Gross Profit		Net Sales		Gross Profit
	Semiconductor products	$	458,298	$	258,646	$	1,366,415	$	766,739
	Technology licensing	24,074		24,074		71,418		71,418
		$	482,372	$	282,720	$	1,437,833	$	838,157
	The following table represents net sales and gross profit for each segment for the three and nine months ended December 31, 2012 (amounts in thousands):
		Three Months Ended				Nine Months Ended
		December 31, 2012				December 31, 2012
		Net Sales		Gross Profit		Net Sales		Gross Profit
	Semiconductor products	$	394,709	$	179,090	$	1,089,738	$	537,679
	Technology licensing	21,338		21,338		61,741		61,741
		$	416,047	$	200,428	$	1,151,479	$	599,420

Investments_Notes

Investments (Notes)	9 Months Ended
	Dec. 31, 2013
Investments [Abstract]	'
Investments	'
	Investments
	The Company's investments are intended to establish a high-quality portfolio that preserves principal, meets liquidity needs, avoids inappropriate concentrations, and delivers an appropriate yield in relationship to the Company's investment guidelines and market conditions.  The following is a summary of available-for-sale securities at December 31, 2013 (amounts in thousands):
		Available-for-sale Securities
		Adjusted		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	Government agency bonds	$	741,492	$	164	$	(5,645	)	$	736,011
	Municipal bonds	51,940		20		(209		)	51,751
	Auction rate securities	9,827		—		—			9,827
	Corporate bonds and debt	857,038		2,858		(1,258		)	858,638
		$	1,660,297	$	3,042	$	(7,112	)	$	1,656,227
	The following is a summary of available-for-sale and marketable equity securities at March 31, 2013 (amounts in thousands):
		Available-for-sale Securities
		Adjusted		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	Government agency bonds	$	558,116	$	335	$	(298	)	$	558,153
	Municipal bonds	25,000		146		(8		)	25,138
	Auction rate securities	33,459		332		—			33,791
	Corporate bonds and debt	680,144		5,137		(159		)	685,122
	Marketable equity securities	5,270		239		—			5,509
		$	1,301,989	$	6,189	$	(465	)	$	1,307,713
	At December 31, 2013, the Company's available-for-sale debt securities are presented on the condensed consolidated balance sheets as short-term investments of $932.3 million and long-term investments of $723.9 million.  At March 31, 2013, the Company’s available-for-sale debt securities and marketable equity securities are presented on the condensed consolidated balance sheets as short-term investments of $1,050.3 million and long-term investments of $257.5 million.
	At December 31, 2013, the Company evaluated its investment portfolio and noted unrealized losses of $7.1 million on its debt securities which were due primarily to higher interest rates and resulting declines in market prices.  Management does not believe any of the unrealized losses represent an other-than-temporary impairment based on its evaluation of available evidence as of December 31, 2013 and the Company's intent is to hold these investments until these assets are no longer impaired, except for certain auction rate securities (ARS).  For those debt securities not scheduled to mature until after December 31, 2014, such recovery is not anticipated to occur in the next year and these investments have been classified as long-term investments.
	The amortized cost and estimated fair value of the available-for-sale securities at December 31, 2013, by contractual maturity, excluding corporate debt of $6.2 million, which has no contractual maturity, are shown below (amounts in thousands).  Expected maturities can differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties, and the Company views its available-for-sale securities as available for current operations.
		Adjusted		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	Available-for-sale
	Due in one year or less	$	190,841	$	721	$	—		$	191,562
	Due after one year and through five years	1,332,690		2,321		(2,223		)	1,332,788
	Due after five years and through ten years	120,749		—		(4,889		)	115,860
	Due after ten years	9,827		—		—			9,827
		$	1,654,107	$	3,042	$	(7,112	)	$	1,650,037
	The Company had no material realized gains or losses from the sale of available-for-sale marketable equity securities or debt securities during each of the three and nine-month periods ended December 31, 2013 and 2012.

Fair_Value_Measurements_Notes

Fair Value Measurements (Notes)	9 Months Ended
	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]	'
Fair Value Measurements	'
	Fair Value Measurements
	Accounting rules for fair value clarify that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants.  As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability.  As a basis for considering such assumptions, the Company utilizes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:
	Level 1-	Observable inputs such as quoted prices in active markets;
	Level 2-	Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and
	Level 3-	Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.
	Marketable Debt Instruments
	Marketable debt instruments include instruments such as corporate bonds and debt, government agency bonds, bank deposits, municipal bonds, and money market fund deposits. When the Company uses observable market prices for identical securities that are traded in less active markets, the Company classifies its marketable debt instruments as Level 2. When observable market prices for identical securities are not available, the Company prices its marketable debt instruments using non-binding market consensus prices that are corroborated with observable market data; quoted market prices for similar instruments; or pricing models, such as a discounted cash flow model, with all significant inputs derived from or corroborated with observable market data. Non-binding market consensus prices are based on the proprietary valuation models of pricing providers or brokers. These valuation models incorporate a number of inputs, including non-binding and binding broker quotes; observable market prices for identical or similar securities; and the internal assumptions of pricing providers or brokers that use observable market inputs and, to a lesser degree, unobservable market inputs. The Company corroborates non-binding market consensus prices with observable market data using statistical models when observable market data exists. The discounted cash flow model uses observable market inputs, such as LIBOR-based yield curves, currency spot and forward rates, and credit ratings.
	Assets and Liabilities Measured at Fair Value on a Recurring Basis
	Assets measured at fair value on a recurring basis at December 31, 2013 are as follows (amounts in thousands):
		Quoted Prices				Significant			Significant				Total
		in Active				Other			Unobservable				Balance
		Markets for				Observable			Inputs
		Identical				Inputs			(Level 3)
		Instruments				(Level 2)
		(Level 1)
	Assets
	Money market mutual funds	$	114,235			$	—		$	—			$	114,235
	Corporate bonds and debt	—				852,448			6,190				858,638
	Government agency bonds	—				736,011			—				736,011
	Deposit accounts	—				260,865			—				260,865
	Municipal bonds	—				51,751			—				51,751
	Auction rate securities	—				—			9,827				9,827
	Total assets measured at fair value	$	114,235			$	1,901,075		$	16,017			$	2,031,327
	Assets and liabilities measured at fair value on a recurring basis at March 31, 2013 are as follows (amounts in thousands):
		Quoted Prices				Significant			Significant				Total
		in Active				Other			Unobservable				Balance
		Markets for Identical Instruments				Observable			Inputs
		(Level 1)				Inputs			(Level 3)
						(Level 2)
	Assets
	Money market fund deposits	$	100,878			$	—		$	—			$	100,878
	Marketable equity securities	5,509				—			—				5,509
	Corporate bonds and debt	—				678,932			6,190				685,122
	Government agency bonds	—				558,153			—				558,153
	Deposit accounts	—				427,456			—				427,456
	Municipal bonds	—				25,138			—				25,138
	Auction rate securities	—				—			33,791				33,791
	Total assets measured at fair value	$	106,387			$	1,689,679		$	39,981			$	1,836,047
	Liabilities
	Contingent consideration	$	—			$	—		$	19,100			$	19,100
	Total liabilities measured at fair value	$	—			$	—		$	19,100			$	19,100
	There were no transfers between Level 1 and Level 2 during the three and nine-month periods ended December 31, 2013 or the year ended March 31, 2013.
	At December 31, 2013, the Company's ARS for which recent auctions were unsuccessful are made up of securities related to the insurance industry valued at $9.8 million. At March 31, 2013, the Company's ARS for which recent auctions were unsuccessful were made up of bonds related to the insurance sector valued at $9.8 million, securities related to the energy and telecommunications sectors valued at $5.3 million, and student loan securities valued at $18.7 million.
	The Company estimated the fair value of its ARS, which are classified as Level 3 securities, based on the following: (i) the underlying structure of each security; (ii) the present value of future principal and interest payments discounted at rates considered to reflect current market conditions; (iii) consideration of the probabilities of default, auction failure, or repurchase at par for each period; and (iv) estimates of the recovery rates in the event of default for each security. The significant unobservable inputs used in the fair value measurement of the insurance sector ARS were estimated risk free discount rates, liquidity risk premium, and the liquidity horizon. The risk free discount rate applied to these securities was 2% to 2.5% adjusted for the liquidity risk premium which ranged from 9.1% to 29.5%. The anticipated liquidity horizon ranged from 7 to 10 years. A significant increase in the liquidity premium or discount rate, in isolation, would lead to a significantly lower fair value measurement. A significant increase in the liquidity horizon, in isolation, would lead to a significantly lower fair value measurement. Each quarter the Company investigates material changes in the fair value measurements of its ARS.
	Level 3 liabilities at March 31, 2013 include contingent consideration from the Company's Roving Networks acquisition, which was fully paid as of December 31, 2013. The Company evaluates the estimated fair value of its contingent consideration on a quarterly basis based on certain revenue and gross margin performance criteria and records fair value adjustments as necessary.
	The following tables present a reconciliation for all assets and liabilities measured at fair value on a recurring basis, excluding accrued interest components, using significant unobservable inputs (Level 3) for the nine months ended December 31, 2013, and the year ended March 31, 2013 (amounts in thousands):
	Nine months ended December 31, 2013		Auction Rate				Corporate			Contingent				Total Gains
			Securities				Debt			Consideration				(Losses)
	Balance at March 31, 2013		$	33,791			$	6,190		$	(19,100	)		$	—
	Total gains (losses) (realized and unrealized):
	Included in earnings		1,103				—			(1,370		)		(267		)
	Included in other comprehensive income		(332		)		—			—				(332		)
	Purchases, sales, issuances, and settlements, net		(24,735		)		—			20,470				—
	Balance at December 31, 2013		$	9,827			$	6,190		$	—			$	(599	)
	Year ended March 31, 2013		Auction Rate				Corporate			Contingent				Total Gains
			Securities				Debt			Consideration				(Losses)
	Balance at March 31, 2012		$	10,246			$	4,625		$	—			$	—
	Total gains (losses) (realized and unrealized):
	Included in earnings		(412		)		—			(4,400		)		$	(4,813	)
	Included in other comprehensive income		332				—			—				332
	Purchases, sales, issuances, and settlements, net		(650		)		1,565			—				—
	Acquisition-related		24,275				—			(14,700		)		—
	Balance at March 31, 2013		$	33,791			$	6,190		$	(19,100	)		$	(4,481	)
Assets measured at fair value on a recurring basis are presented/classified on the condensed consolidated balance sheets at December 31, 2013 as follows (amounts in thousands):
	Quoted Prices				Significant			Significant				Total
	in Active				Other			Unobservable				Balance
	Markets for				Observable			Inputs
	Identical				Inputs			(Level 3)
	Instruments				(Level 2)
	(Level 1)
Assets
Cash and cash equivalents	$	114,235			$	260,865		$	—			$	375,100
Short-term investments	—				932,302			—				932,302
Long-term investments	—				707,908			16,017				723,925
Total assets measured at fair value	$	114,235			$	1,901,075		$	16,017			$	2,031,327
Assets measured at fair value on a recurring basis are presented/classified in the consolidated balance sheets at March 31, 2013 as follows (amounts in thousands):
	Quoted Prices				Significant			Significant				Total
	in Active				Other			Unobservable				Balance
	Markets for				Observable			Inputs
	Identical				Inputs			(Level 3)
	Instruments				(Level 2)
	(Level 1)
Assets
Cash and cash equivalents	$	100,878			$	427,456		$	—			$	528,334
Short-term investments	—				1,050,263			—				1,050,263
Long-term investments	5,509				211,960			39,981				257,450
Total assets measured at fair value	$	106,387			$	1,689,679		$	39,981			$	1,836,047
Financial Assets Not Recorded at Fair Value on a Recurring Basis
The Company's non-marketable equity and cost-method investments are not recorded at fair value on a recurring basis.  These investments are monitored on a quarterly basis for impairment charges.  The investments will only be recorded at fair value when an impairment charge is recognized.  There were no impairment charges recognized on these investments in the three and nine months ended December 31, 2013. The Company recognized impairment charges of $0.5 million during the three and nine months ended December 31, 2012. These investments are included in other assets on the condensed consolidated balance sheet.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments (Notes)	9 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Instruments	'
	Fair Value of Financial Instruments
	The carrying amount of cash equivalents approximates fair value because their maturity is less than three months.  Management believes the carrying amount of the equity and cost-method investments materially approximated fair value at December 31, 2013 based upon unobservable inputs. The fair values of these investments have been determined as Level 3 fair value measurements. The fair values of the Company's line of credit and short-term and long-term borrowings are estimated using discounted cash flow analyses, based on the Company's current incremental borrowing rates for similar types of borrowing arrangements and approximate carrying value. Based on the borrowing rates currently available to the Company for bank loans with similar terms and average maturities, the fair value of the Company's line of credit and long-term borrowings at December 31, 2013 approximated book value and are considered Level 2 in the fair value hierarchy described in Note 8. The carrying amount of accounts receivable, accounts payable and accrued liabilities approximates fair value due to the short-term maturity of the amounts.  The fair value of the Company's junior subordinated convertible debentures was $1.987 billion at December 31, 2013 and $1.639 billion at March 31, 2013 based on observable market prices for these debentures, which are traded in less active markets and are therefore classified as a Level 2 fair value measurement.

Accounts_Receivable_Notes

Accounts Receivable (Notes)	9 Months Ended
	Dec. 31, 2013
Accounts Receivable, Net [Abstract]	'
Accounts Receivable	'
	Accounts Receivable
	Accounts receivable consists of the following (amounts in thousands):
		December 31, 2013		March 31, 2013
	Trade accounts receivable	$	224,832	$	230,469
	Other	2,102		2,250
		226,934		232,719
	Less allowance for doubtful accounts	2,661		2,764
		$	224,273	$	229,955

Inventories_Notes

Inventories (Notes)	9 Months Ended
	Dec. 31, 2013
Inventory, Net [Abstract]	'
Inventories	'
	Inventories
	The components of inventories consist of the following (amounts in thousands):
		December 31, 2013		March 31, 2013
	Raw materials	$	9,555	$	9,020
	Work in process	187,822		181,750
	Finished goods	77,252		51,564
		$	274,629	$	242,334
	Inventories are valued at the lower of cost or market using the first-in, first-out method. Inventory impairment charges establish a new cost basis for inventory and charges are not subsequently reversed to income even if circumstances later suggest that increased carrying amounts are recoverable.

Property_Plant_and_Equipment_N

Property, Plant and Equipment (Notes)	9 Months Ended
	Dec. 31, 2013
Property, Plant and Equipment [Abstract]	'
Property, Plant and Equipment Disclosure [Text Block]	'
	Property, Plant and Equipment
	Property, plant and equipment consists of the following (amounts in thousands):
		December 31, 2013		March 31, 2013
	Land	$	55,601	$	47,102
	Building and building improvements	407,520		396,611
	Machinery and equipment	1,442,169		1,377,814
	Projects in process	62,217		76,158
		1,967,507		1,897,685
	Less accumulated depreciation and amortization	1,446,942		1,383,141
		$	520,565	$	514,544
	Depreciation expense attributed to property, plant and equipment was $22.2 million and $66.7 million for the three and nine months ended December 31, 2013, respectively, and $23.0 million and $66.0 million for the three and nine months ended December 31, 2012, respectively.

Accrued_Liabilities_Notes

Accrued Liabilities (Notes)	9 Months Ended
	Dec. 31, 2013
Liabilities, Current [Abstract]	'
Accrued liabilities	'
	Accrued Liabilities
	Accrued liabilities consist of the following (amounts in thousands):
		December 31, 2013		March 31, 2013
	Acquisition related contingent consideration	$	—	$	19,100
	Other accrued expenses	96,176		108,008
		$	96,176	$	127,108

Income_taxes_Notes

Income taxes (Notes)	9 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The provision for income taxes reflects tax on foreign earnings and federal and state tax on U.S. earnings.  The Company had an effective tax rate of 9.7% for the nine-month period ended December 31, 2013 and 34.1% for the nine-month period ended December 31, 2012.  During the three and nine months ended December 31, 2013, the Company recognized a net $6.2 million one-time tax benefit associated with a favorable settlement of an IRS examination for fiscal years 2009 and 2010 offset by unfavorable items associated with the filing of the Company's fiscal 2013 tax returns as compared to its year-end tax provisions. The Company's effective tax rate is lower than statutory rates in the U.S. due primarily to its mix of earnings in foreign jurisdictions with lower tax rates and the aforementioned net tax benefit. The Company's effective tax rate was higher in the December 31, 2012 period due to certain tax expenses associated with the acquisition of SMSC.
	At December 31, 2013, the Company had $179.2 million of unrecognized tax benefits.  Unrecognized tax benefits decreased by $3.5 million compared to March 31, 2013 primarily as a result of the release of accruals related to the settlement of an IRS audit offset by the ongoing accrual for uncertain tax positions and the accrual of deficiency interest on these positions.
	The Company files U.S. federal, U.S. state, and foreign income tax returns.  For U.S. federal, and in general for U.S. state tax returns, the fiscal 2011 and later tax years remain open for examination by tax authorities.  The IRS is currently auditing SMSC's 2011 and 2012 tax years.  For foreign tax returns, the Company is generally no longer subject to income tax examinations for years prior to fiscal 2005.
	The Company recognizes liabilities for anticipated tax audit issues in the U.S. and other tax jurisdictions based on its estimate of whether, and the extent to which, additional tax payments are more likely than not.  The Company believes that it has appropriate support for the income tax positions taken on its tax returns and that its accruals for tax liabilities are adequate for all open years based on an assessment of many factors including past experience and interpretations of tax laws applied to the facts of each matter.
	The Company believes that it maintains appropriate reserves to offset any potential income tax liabilities that may arise upon final resolution of matters for open tax years.  If such reserve amounts ultimately prove to be unnecessary, the resulting reversal of such reserves would result in tax benefits being recorded in the period the reserves are no longer deemed necessary.  If such amounts prove to be less than an ultimate assessment, a future charge to expense would be recorded in the period in which the assessment is determined.  Although the timing of the resolution and/or closure of audits is highly uncertain, the Company does not believe it is reasonably possible that its unrecognized tax benefits would materially change in the next 12 months.

2125_Junior_subordinated_conve

2.125% Junior subordinated convertible debentures (Notes)	9 Months Ended
	Dec. 31, 2013
Convertible Debt [Abstract]	'
Junior subordinated convertible debentures	'
	2.125% Junior Subordinated Convertible Debentures
	The Company's $1.15 billion principal amount of 2.125% junior subordinated convertible debentures due December 15, 2037, are subordinated in right of payment to any future senior debt of the Company and are effectively subordinated in right of payment to the liabilities of the Company's subsidiaries.  The debentures are convertible, subject to certain conditions, into shares of the Company's common stock at an initial conversion rate of 29.2783 shares of common stock per $1,000 principal amount of debentures, representing an initial conversion price of approximately $34.16 per share of common stock.  As of December 31, 2013, the holders of the debentures had the right to convert their debentures between October 1, 2013 and December 31, 2013 because for at least 20 trading days during the 30 consecutive trading day period ending on December 31, 2013, the Company's common stock had a last reported sale price greater than 130% of the conversion price. As of December 31, 2013, a holder could realize more economic value by selling its debentures in the over the counter market than from converting its debentures. As a result of cash dividends paid since the issuance of the debentures, the conversion rate has been adjusted to 38.3572 shares of common stock per $1,000 of principal amount of debentures, representing a conversion price of approximately $26.07 per share of common stock.
	As the debentures can be settled in cash upon conversion, for accounting purposes, the debentures were bifurcated into a liability component and an equity component, which are both initially recorded at fair value.  The carrying value of the equity component at December 31, 2013 and at March 31, 2013 was $822.4 million.  The estimated fair value of the liability component of the debentures at the issuance date was $327.6 million, resulting in a debt discount of $822.4 million.  The unamortized debt discount was $779.5 million at December 31, 2013 and $786.2 million at March 31, 2013.  The carrying value of the debentures was $369.6 million at December 31, 2013 and $363.4 million at March 31, 2013.  The remaining period over which the unamortized debt discount will be recognized as non-cash interest expense is 24 years.  In the three and nine months ended December 31, 2013, the Company recognized $2.3 million and $6.7 million, respectively, in non-cash interest expense related to the amortization of the debt discount.  In the three and nine months ended December 31, 2012, the Company recognized $2.1 million and $6.1 million, respectively, in non-cash interest expense related to the amortization of the debt discount.  The Company recognized $6.1 million and $18.3 million of interest expense related to the 2.125% coupon on the debentures in each of the three and nine-month periods ended December 31, 2013 and December 31, 2012, respectively.

Credit_facility_Notes

Credit facility (Notes)	9 Months Ended
	Dec. 31, 2013
Credit Facility [Abstract]	'
Credit Facility	'
	Credit Facility
	On June 27, 2013, the Company entered into a $2.0 billion credit agreement among the Company, the lenders from time to time that are parties thereto and JPMorgan Chase Bank, N.A., as administrative agent (the Credit Agreement). The Credit Agreement provides for a $350 million term loan and a $1.65 billion revolving credit facility, with a $125 million foreign currency sublimit, a $35 million letter of credit sublimit and a $25 million swingline loan sublimit, terminating on June 27, 2018 (the Maturity Date). The Credit Agreement also contains an increase option permitting the Company, subject to certain requirements, to arrange with existing lenders and/or new lenders for them to provide up to an aggregate of $300 million in additional commitments, which may be for revolving loans or term loans. Proceeds of loans made under the Credit Agreement may be used for working capital and general corporate purposes. The Credit Agreement replaced another credit agreement the Company had in place since August 2011. At December 31, 2013, $650.0 million of borrowings were outstanding under the Credit Agreement consisting of $300.0 million of a revolving line of credit and $350.0 million of a term loan, net of $1.2 million of debt discount resulting from amounts paid to the lenders.
	The loans under the Credit Agreement bear interest, at the Company's option, at the base rate plus a spread of 0.25% to 1.25% or an adjusted LIBOR rate (based on one, two, three, or six-month interest periods) plus a spread of 1.25% to 2.25%, in each case with such spread being determined based on the consolidated leverage ratio for the preceding four fiscal quarter period. The base rate means the highest of JPMorgan Chase Bank, N.A.'s prime rate, the federal funds rate plus a margin equal to 0.50% and the adjusted LIBOR rate for a 1-month interest period plus a margin equal to 1.00%. Swingline loans accrue interest at a per annum rate based on the base rate plus the applicable margin for base rate loans. Base rate loans may only be made in U.S. dollars. The Company is also obligated to pay other customary administration fees and letter of credit fees for a credit facility of this size and type.
	Interest is due and payable in arrears quarterly for loans bearing interest at the base rate and at the end of an interest period (or at each three-month interval in the case of loans with interest periods greater than three months) in the case of loans bearing interest at the adjusted LIBOR rate. Interest expense related to the Credit Agreement was approximately $4.1 million in the three months ended December 31, 2013 and $11.5 million in the nine months ended December 31, 2013. Interest expense related to the Company's prior credit agreement was approximately $3.1 million and $6.1 million in the three and nine months ended December 31, 2012, respectively. Principal, together with all accrued and unpaid interest, is due and payable on the Maturity Date. The Company may prepay the loans and terminate the commitments, in whole or in part, at any time without premium or penalty, subject to certain conditions including minimum amounts in the case of commitment reductions and reimbursement of certain costs in the case of prepayments of LIBOR loans.
	The Company's obligations under the Credit Agreement are guaranteed by certain of its subsidiaries meeting materiality thresholds set forth in the Credit Agreement. To secure the Company's obligations under the Credit Agreement, the Company and its domestic subsidiaries will be required to pledge the equity securities of certain of their respective material subsidiaries, subject to certain exceptions and limitations.
	The Credit Agreement contains customary affirmative and negative covenants, including covenants that limit or restrict the Company and its subsidiaries' ability to, among other things, incur subsidiary indebtedness, grant liens, merge or consolidate, dispose of assets, make investments, make acquisitions, enter into certain transactions with affiliates, pay dividends or make distributions, repurchase stock, enter into restrictive agreements and enter into sale and leaseback transactions, in each case subject to customary exceptions for a credit facility of this size and type. The Company is also required to maintain compliance with a consolidated leverage ratio and a consolidated interest coverage ratio. At December 31, 2013, the Company was in compliance with these covenants.
	The Credit Agreement includes customary events of default that include, among other things, non-payment defaults, inaccuracy of representations and warranties, covenant defaults, cross default to material indebtedness, bankruptcy and insolvency defaults, material judgment defaults, ERISA defaults and a change of control default. The occurrence of an event of default could result in the acceleration of the obligations under the Credit Agreement. Under certain circumstances, a default interest rate will apply on all obligations during the existence of an event of default under the Credit Agreement at a per annum rate equal to 2.00% above the applicable interest rate for any overdue principal and 2.00% above the rate applicable for base rate loans for any other overdue amounts.

Contingencies_Notes

Contingencies (Notes)	9 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Contingencies	'
	Contingencies
	In the ordinary course of the Company's business, it is involved in a limited number of legal actions, both as plaintiff and defendant, and could incur uninsured liability in any one or more of them.  The Company also periodically receives notifications from various third parties alleging infringement of patents, intellectual property rights or other matters.  With respect to pending legal actions to which the Company is a party, although the outcomes of these actions are not generally determinable, the Company believes that the ultimate resolution of these matters will not have a material adverse effect on its financial position, cash flows or results of operations.  Litigation relating to the semiconductor industry is not uncommon, and the Company is, and from time to time has been, subject to such litigation.  No assurances can be given with respect to the extent or outcome of any such litigation in the future.
	The Company's technology license agreements generally include an indemnification clause that indemnifies the licensee against liability and damages (including legal defense costs) arising from any claims of patent, copyright, trademark or trade secret infringement by the Company's proprietary technology.  The terms of these indemnification provisions approximate the terms of the outgoing technology license agreements, which are typically perpetual unless terminated by either party for breach.  The possible amount of future payments the Company could be required to make based on agreements that specify indemnification limits, if such indemnifications were required on all of these agreements, is approximately $121 million. There are some licensing agreements in place that do not specify indemnification limits.  The Company had not recorded any liabilities related to these indemnification obligations as of December 31, 2013.
	Contingent liabilities in the amount of $13.0 million were recorded in connection with the Company's April 8, 2010 acquisition of Silicon Storage Technology Inc. (SST) as an adverse outcome was determined to be probable and estimable.  One of the contingent liabilities associated with the SST acquisition was resolved in the second quarter of fiscal 2013 with legal settlement costs of approximately $11.5 million for certain legal matters related to SST in excess of previously accrued amounts, which were expensed as special charges in the statement of income. At December 31, 2013, $5.7 million of the original contingent liabilities recorded were still outstanding.

Derivative_Instruments_Notes

Derivative Instruments (Notes)	9 Months Ended
	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Instruments and Hedging Activities Disclosure [Text Block]	'
	Derivative Instruments
	The Company has international operations and is thus subject to foreign currency rate fluctuations.  To help manage the risk of changes in foreign currency rates, the Company periodically enters into derivative contracts comprised of foreign currency forward contracts to hedge its asset and liability foreign currency exposure and a portion of its foreign currency operating expenses.  Approximately 99% of the Company's sales are U.S. dollar denominated.  To date, the exposure related to foreign exchange rate volatility has not been material to the Company's operating results.  As of December 31, 2013, the Company had no foreign currency forward contracts outstanding. As of March 31, 2013, the Company had foreign currency forward contracts with notional amounts of $6.0 million to economically hedge certain balance sheet exposures related to the Japanese yen. As these contracts were executed at or near the end of the respective periods, there were no unrecognized gains or losses on these contracts at March 31, 2013. The Company recognized an immaterial amount of net realized gains and losses on foreign currency forward contracts in each of the three and nine months ended December 31, 2013 and 2012. Gains and losses from changes in the fair value of these foreign currency forward contracts are credited or charged to Other Income (Expense). The Company does not apply hedge accounting to its foreign currency derivative instruments.

Comprehensive_Income_Notes

Comprehensive Income (Notes)	9 Months Ended
	Dec. 31, 2013
Other Comprehensive Income (Loss), Net of Tax [Abstract]	'
Comprehensive Income	'
	Comprehensive Income
	The following table presents the changes in the components of accumulated other comprehensive income (AOCI) for the nine months ended December 31, 2013 (amounts in thousands):
		Unrealized			Minimum			Foreign				Total
		holding gains (losses)			pension			Currency
		available-for-sale securities			liability
	Balance at March 31, 2013	$	5,444		$	52		$	1,439			$	6,935
	Other comprehensive loss before reclassifications	(8,011		)	—			—				(8,011		)
	Amounts reclassified from accumulated other comprehensive income (loss)	(1,503		)	—			—				(1,503		)
	Net other comprehensive loss	(9,514		)	—			—				(9,514		)
	Balance at December 31, 2013	$	(4,070	)	$	52		$	1,439			$	(2,579	)
	The table below details where reclassifications of realized transactions out of AOCI are recorded on the Consolidated Statements of Income.
			Three Months Ended						Nine Months Ended
			December 31,						December 31,
	Description of AOCI Component		2013			2012			2013				2012			Related Statement
																of Income Line
	Unrealized gains on available-for-sale securities		$	113		$	14		$	2,279			$	235		Other income
	Taxes		—			—			(776		)		(51		)	Provision for income taxes
	Reclassification of realized transactions, net of taxes		$	113		$	14		$	1,503			$	184		Net Income

ShareBased_Compensation_Notes

Share-Based Compensation (Notes)	9 Months Ended
	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Equity incentive plans	'
	Share-Based Compensation
	The following table presents the details of the Company's share-based compensation expense (amounts in thousands):
		Three Months Ended						Nine Months Ended
		December 31,						December 31,
		2013			2012			2013			2012
	Cost of sales	$	1,841	(1)	$	1,834	(1)	$	5,674	(1)	$	5,758	(1)
	Research and development	6,141			6,172			18,762			16,562
	Selling, general and administrative	5,737			6,114			16,939			22,339
	Pre-tax effect of share-based compensation	13,719			14,120			41,375			44,659
	Income tax benefit	1,510			2,755			4,501			7,496
	Net income effect of share-based compensation	$	12,209		$	11,365		$	36,874		$	37,163
	(1) During the three and nine months ended December 31, 2013, $1.9 million and $5.7 million, respectively, of share-based compensation expense was capitalized to inventory and $1.8 million and $5.7 million, respectively, of previously capitalized share-based compensation expenses in inventory was sold.  During the three and nine months ended December 31, 2012, $1.8 million and $5.3 million, respectively, of share-based compensation expense was capitalized to inventory and $1.8 million and $5.8 million, respectively, of previously capitalized share-based compensation expense in inventory was sold.

Net_income_per_common_share_No

Net income per common share (Notes)	9 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Net income per common share	'
	Net Income Per Common Share
	The following table sets forth the computation of basic and diluted net income per common share (in thousands, except per share amounts):
		Three Months Ended				Nine Months Ended
		December 31,				December 31,
		2013		2012		2013		2012
	Net income	$	105,401	$	10,173	$	283,786	$	67,699
	Weighted average common shares outstanding	198,759		194,958		197,845		194,157
	Dilutive effect of stock options and RSUs	3,834		3,725		3,882		3,709
	Dilutive effect of convertible debt	16,496		5,722		14,216		6,687
	Weighted average common and potential common shares outstanding	219,089		204,405		215,943		204,553
	Basic net income per common share	$	0.53	$	0.05	$	1.43	$	0.35
	Diluted net income per common share	$	0.48	$	0.05	$	1.31	$	0.33
	Diluted net income per common share for the three and nine months ended December 31, 2013 includes 16,496,384 shares and 14,215,573 shares, respectively, issuable upon the exchange of debentures (see Note 15).  Diluted net income per common share for the three and nine months ended December 31, 2012 includes 5,721,774 and 6,687,078 shares, respectively, issuable upon the exchange of debentures.  The debentures have no impact on diluted net income per common share unless the average price of the Company's common stock exceeds the conversion price because the principal amount of the debentures will be settled in cash upon conversion.  Prior to conversion, the Company will include, in the diluted net income per common share calculation, the effect of the additional shares that may be issued when the Company's common stock price exceeds the conversion price using the treasury stock method.  The weighted average conversion price per share used in calculating the dilutive effect of the convertible debt for the three and nine-month periods ended December 31, 2013 was $26.19 and $26.43, respectively. The weighted average conversion price per share used in calculating the dilutive effect of the convertible debt for the three and nine-month period ended December 31, 2012 was $27.21 and $27.51, respectively.
	Weighted average common shares exclude the effect of option shares which are not dilutive.  There were no antidilutive option shares for the three and nine months ended December 31, 2013. For the three and nine months ended December 31, 2012, the number of option shares that were antidilutive was 124,395 and 110,021, respectively.

Dividends_Notes

Dividends (Notes)	9 Months Ended
	Dec. 31, 2013
Dividends [Abstract]	'
Dividends [Text Block]	'
	Dividends
	A quarterly cash dividend of $0.3545 per share was paid on December 5, 2013 in the aggregate amount of $70.6 million.  Through the first nine months of fiscal 2014, cash dividends of $1.062 per share have been paid in the aggregate of $210.3 million. A quarterly cash dividend of $0.355 per share was declared on January 30, 2014 and will be paid on March 7, 2014 to stockholders of record as of February 21, 2014. The Company expects the March 2014 payment of its quarterly cash dividend to be approximately $70.7 million.

Reclassification_of_Prior_Peri1

Reclassification of Prior Periods (Tables)	9 Months Ended
	Dec. 31, 2013
Accounting Changes and Error Corrections [Abstract]	'
Schedule of Error Corrections and Prior Period Adjustments	'
	The effect on net cash provided by operating activities and net cash used in investing activities for the previous period covered by this report are shown below (amounts in thousands):
		Nine Months Ended
		31-Dec-12
		As reported			Adjustment			As adjusted
	Cash flows from operating activities
	Amortization of premium on available-for-sale investments	$	—		$	10,304		$	10,304
	Net cash provided by operating activities	321,178			10,304			331,482
	Cash flows from investing activities
	Purchases of available-for-sale investments	(646,424		)	(10,304		)	(656,728		)
	Net cash used in investing activities	(920,807		)	(10,304		)	(931,111		)

Business_Acquisitions_Tables

Business Acquisitions (Tables)	9 Months Ended
	Dec. 31, 2013
Business Combinations [Abstract]	'
Schedule of Purchase Price Allocation [Table Text Block]	'
	The table below represents the allocation of the purchase price, including adjustments to the purchase price allocation from the previously reported figures at March 31, 2013, to the net assets acquired based on their estimated fair values as of August 2, 2012. The purchase price allocation was finalized as of August 2, 2013. All adjustments shown in the table below were recorded during the three months ended June 30, 2013 (amounts in thousands):
	Assets acquired	Previously Reported			Adjustments			31-Dec-13
		31-Mar-13
	Cash and cash equivalents	$	180,925		$	—		$	180,925
	Accounts receivable, net	58,441			—			58,441
	Inventories	86,244			—			86,244
	Prepaid expenses	5,617			—			5,617
	Deferred tax assets	15,843			—			15,843
	Other current assets	17,578			—			17,578
	Property, plant and equipment, net	35,608			—			35,608
	Long-term investments	24,275			—			24,275
	Goodwill	169,065			(3,473		)	165,592
	Intangible assets, net	10,214			—			10,214
	Purchased intangible assets	517,800			—			517,800
	Other assets	3,835			—			3,835
	Total assets acquired	1,125,445			(3,473		)	1,121,972
	Liabilities assumed
	Accounts payable	(28,035		)	—			(28,035		)
	Accrued liabilities	(62,038		)	(209		)	(62,247		)
	Deferred income on shipments to distributors	(11,376		)	—			(11,376		)
	Long-term income tax payable	(72,781		)	—			(72,781		)
	Deferred tax liability	(21,079		)	4,397			(16,682		)
	Other liabilities	(10,535		)	(715		)	(11,250		)
	Total liabilities assumed	(205,844		)	3,473			(202,371		)
	Purchase price allocated	$	919,601		$	—		$	919,601

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Dec. 31, 2013
Segment Reporting [Abstract]	'
Revenues and gross profit for each segment	'
	The following table represents net sales and gross profit for each segment for the three and nine months ended December 31, 2013 (amounts in thousands):
		Three Months Ended				Nine Months Ended
		December 31, 2013				December 31, 2013
		Net Sales		Gross Profit		Net Sales		Gross Profit
	Semiconductor products	$	458,298	$	258,646	$	1,366,415	$	766,739
	Technology licensing	24,074		24,074		71,418		71,418
		$	482,372	$	282,720	$	1,437,833	$	838,157
	The following table represents net sales and gross profit for each segment for the three and nine months ended December 31, 2012 (amounts in thousands):
		Three Months Ended				Nine Months Ended
		December 31, 2012				December 31, 2012
		Net Sales		Gross Profit		Net Sales		Gross Profit
	Semiconductor products	$	394,709	$	179,090	$	1,089,738	$	537,679
	Technology licensing	21,338		21,338		61,741		61,741
		$	416,047	$	200,428	$	1,151,479	$	599,420

Investments_Tables

Investments (Tables)	9 Months Ended
	Dec. 31, 2013
Investments [Abstract]	'
Summary of available-for-sale securities	'
	The following is a summary of available-for-sale securities at December 31, 2013 (amounts in thousands):
		Available-for-sale Securities
		Adjusted		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	Government agency bonds	$	741,492	$	164	$	(5,645	)	$	736,011
	Municipal bonds	51,940		20		(209		)	51,751
	Auction rate securities	9,827		—		—			9,827
	Corporate bonds and debt	857,038		2,858		(1,258		)	858,638
		$	1,660,297	$	3,042	$	(7,112	)	$	1,656,227
	The following is a summary of available-for-sale and marketable equity securities at March 31, 2013 (amounts in thousands):
		Available-for-sale Securities
		Adjusted		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	Government agency bonds	$	558,116	$	335	$	(298	)	$	558,153
	Municipal bonds	25,000		146		(8		)	25,138
	Auction rate securities	33,459		332		—			33,791
	Corporate bonds and debt	680,144		5,137		(159		)	685,122
	Marketable equity securities	5,270		239		—			5,509
		$	1,301,989	$	6,189	$	(465	)	$	1,307,713
Summary of amortized cost and estimated fair value of available-for-sale securities, by maturity	'
	The amortized cost and estimated fair value of the available-for-sale securities at December 31, 2013, by contractual maturity, excluding corporate debt of $6.2 million, which has no contractual maturity, are shown below (amounts in thousands).  Expected maturities can differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties, and the Company views its available-for-sale securities as available for current operations.
		Adjusted		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	Available-for-sale
	Due in one year or less	$	190,841	$	721	$	—		$	191,562
	Due after one year and through five years	1,332,690		2,321		(2,223		)	1,332,788
	Due after five years and through ten years	120,749		—		(4,889		)	115,860
	Due after ten years	9,827		—		—			9,827
		$	1,654,107	$	3,042	$	(7,112	)	$	1,650,037

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]	'
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	'
	Assets measured at fair value on a recurring basis at December 31, 2013 are as follows (amounts in thousands):
		Quoted Prices				Significant			Significant				Total
		in Active				Other			Unobservable				Balance
		Markets for				Observable			Inputs
		Identical				Inputs			(Level 3)
		Instruments				(Level 2)
		(Level 1)
	Assets
	Money market mutual funds	$	114,235			$	—		$	—			$	114,235
	Corporate bonds and debt	—				852,448			6,190				858,638
	Government agency bonds	—				736,011			—				736,011
	Deposit accounts	—				260,865			—				260,865
	Municipal bonds	—				51,751			—				51,751
	Auction rate securities	—				—			9,827				9,827
	Total assets measured at fair value	$	114,235			$	1,901,075		$	16,017			$	2,031,327
	Assets and liabilities measured at fair value on a recurring basis at March 31, 2013 are as follows (amounts in thousands):
		Quoted Prices				Significant			Significant				Total
		in Active				Other			Unobservable				Balance
		Markets for Identical Instruments				Observable			Inputs
		(Level 1)				Inputs			(Level 3)
						(Level 2)
	Assets
	Money market fund deposits	$	100,878			$	—		$	—			$	100,878
	Marketable equity securities	5,509				—			—				5,509
	Corporate bonds and debt	—				678,932			6,190				685,122
	Government agency bonds	—				558,153			—				558,153
	Deposit accounts	—				427,456			—				427,456
	Municipal bonds	—				25,138			—				25,138
	Auction rate securities	—				—			33,791				33,791
	Total assets measured at fair value	$	106,387			$	1,689,679		$	39,981			$	1,836,047
	Liabilities
	Contingent consideration	$	—			$	—		$	19,100			$	19,100
	Total liabilities measured at fair value	$	—			$	—		$	19,100			$	19,100
Reconciliation of assets and liabilities measured at fair value on a recurring basis	'
	The following tables present a reconciliation for all assets and liabilities measured at fair value on a recurring basis, excluding accrued interest components, using significant unobservable inputs (Level 3) for the nine months ended December 31, 2013, and the year ended March 31, 2013 (amounts in thousands):
	Nine months ended December 31, 2013		Auction Rate				Corporate			Contingent				Total Gains
			Securities				Debt			Consideration				(Losses)
	Balance at March 31, 2013		$	33,791			$	6,190		$	(19,100	)		$	—
	Total gains (losses) (realized and unrealized):
	Included in earnings		1,103				—			(1,370		)		(267		)
	Included in other comprehensive income		(332		)		—			—				(332		)
	Purchases, sales, issuances, and settlements, net		(24,735		)		—			20,470				—
	Balance at December 31, 2013		$	9,827			$	6,190		$	—			$	(599	)
	Year ended March 31, 2013		Auction Rate				Corporate			Contingent				Total Gains
			Securities				Debt			Consideration				(Losses)
	Balance at March 31, 2012		$	10,246			$	4,625		$	—			$	—
	Total gains (losses) (realized and unrealized):
	Included in earnings		(412		)		—			(4,400		)		$	(4,813	)
	Included in other comprehensive income		332				—			—				332
	Purchases, sales, issuances, and settlements, net		(650		)		1,565			—				—
	Acquisition-related		24,275				—			(14,700		)		—
	Balance at March 31, 2013		$	33,791			$	6,190		$	(19,100	)		$	(4,481	)
Fair Value, by Balance Sheet Grouping	'
	Assets measured at fair value on a recurring basis are presented/classified on the condensed consolidated balance sheets at December 31, 2013 as follows (amounts in thousands):
		Quoted Prices				Significant			Significant				Total
		in Active				Other			Unobservable				Balance
		Markets for				Observable			Inputs
		Identical				Inputs			(Level 3)
		Instruments				(Level 2)
		(Level 1)
	Assets
	Cash and cash equivalents	$	114,235			$	260,865		$	—			$	375,100
	Short-term investments	—				932,302			—				932,302
	Long-term investments	—				707,908			16,017				723,925
	Total assets measured at fair value	$	114,235			$	1,901,075		$	16,017			$	2,031,327
	Assets measured at fair value on a recurring basis are presented/classified in the consolidated balance sheets at March 31, 2013 as follows (amounts in thousands):
		Quoted Prices				Significant			Significant				Total
		in Active				Other			Unobservable				Balance
		Markets for				Observable			Inputs
		Identical				Inputs			(Level 3)
		Instruments				(Level 2)
		(Level 1)
	Assets
	Cash and cash equivalents	$	100,878			$	427,456		$	—			$	528,334
	Short-term investments	—				1,050,263			—				1,050,263
	Long-term investments	5,509				211,960			39,981				257,450
	Total assets measured at fair value	$	106,387			$	1,689,679		$	39,981			$	1,836,047

Accounts_Receivable_Tables

Accounts Receivable (Tables)	9 Months Ended
	Dec. 31, 2013
Accounts Receivable, Net [Abstract]	'
Accounts Receivable Schedule	'
	Accounts receivable consists of the following (amounts in thousands):
		December 31, 2013		March 31, 2013
	Trade accounts receivable	$	224,832	$	230,469
	Other	2,102		2,250
		226,934		232,719
	Less allowance for doubtful accounts	2,661		2,764
		$	224,273	$	229,955

Inventories_Tables

Inventories (Tables)	9 Months Ended
	Dec. 31, 2013
Inventory, Net [Abstract]	'
Components of inventories	'
	The components of inventories consist of the following (amounts in thousands):
		December 31, 2013		March 31, 2013
	Raw materials	$	9,555	$	9,020
	Work in process	187,822		181,750
	Finished goods	77,252		51,564
		$	274,629	$	242,334

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	9 Months Ended
	Dec. 31, 2013
Property, Plant and Equipment [Abstract]	'
Property, Plant and Equipment	'
	Property, plant and equipment consists of the following (amounts in thousands):
		December 31, 2013		March 31, 2013
	Land	$	55,601	$	47,102
	Building and building improvements	407,520		396,611
	Machinery and equipment	1,442,169		1,377,814
	Projects in process	62,217		76,158
		1,967,507		1,897,685
	Less accumulated depreciation and amortization	1,446,942		1,383,141
		$	520,565	$	514,544

Accrued_Liabilities_Tables

Accrued Liabilities (Tables)	9 Months Ended
	Dec. 31, 2013
Liabilities, Current [Abstract]	'
Accrued liabilities	'
	Accrued liabilities consist of the following (amounts in thousands):
		December 31, 2013		March 31, 2013
	Acquisition related contingent consideration	$	—	$	19,100
	Other accrued expenses	96,176		108,008
		$	96,176	$	127,108

Comprehensive_Income_Tables

Comprehensive Income (Tables)	9 Months Ended
	Dec. 31, 2013
Other Comprehensive Income (Loss), Net of Tax [Abstract]	'
Schedule of Accumulated Other Comprehensive Income (Loss)	'
	The following table presents the changes in the components of accumulated other comprehensive income (AOCI) for the nine months ended December 31, 2013 (amounts in thousands):
		Unrealized			Minimum			Foreign				Total
		holding gains (losses)			pension			Currency
		available-for-sale securities			liability
	Balance at March 31, 2013	$	5,444		$	52		$	1,439			$	6,935
	Other comprehensive loss before reclassifications	(8,011		)	—			—				(8,011		)
	Amounts reclassified from accumulated other comprehensive income (loss)	(1,503		)	—			—				(1,503		)
	Net other comprehensive loss	(9,514		)	—			—				(9,514		)
	Balance at December 31, 2013	$	(4,070	)	$	52		$	1,439			$	(2,579	)
Reclassification out of Accumulated Other Comprehensive Income	'
	The table below details where reclassifications of realized transactions out of AOCI are recorded on the Consolidated Statements of Income.
			Three Months Ended						Nine Months Ended
			December 31,						December 31,
	Description of AOCI Component		2013			2012			2013				2012			Related Statement
																of Income Line
	Unrealized gains on available-for-sale securities		$	113		$	14		$	2,279			$	235		Other income
	Taxes		—			—			(776		)		(51		)	Provision for income taxes
	Reclassification of realized transactions, net of taxes		$	113		$	14		$	1,503			$	184		Net Income

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	9 Months Ended
	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Share-based compensation expense	'
	The following table presents the details of the Company's share-based compensation expense (amounts in thousands):
		Three Months Ended						Nine Months Ended
		December 31,						December 31,
		2013			2012			2013			2012
	Cost of sales	$	1,841	(1)	$	1,834	(1)	$	5,674	(1)	$	5,758	(1)
	Research and development	6,141			6,172			18,762			16,562
	Selling, general and administrative	5,737			6,114			16,939			22,339
	Pre-tax effect of share-based compensation	13,719			14,120			41,375			44,659
	Income tax benefit	1,510			2,755			4,501			7,496
	Net income effect of share-based compensation	$	12,209		$	11,365		$	36,874		$	37,163

Net_income_per_common_share_Ta

Net income per common share (Tables)	9 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	'
	The following table sets forth the computation of basic and diluted net income per common share (in thousands, except per share amounts):
		Three Months Ended				Nine Months Ended
		December 31,				December 31,
		2013		2012		2013		2012
	Net income	$	105,401	$	10,173	$	283,786	$	67,699
	Weighted average common shares outstanding	198,759		194,958		197,845		194,157
	Dilutive effect of stock options and RSUs	3,834		3,725		3,882		3,709
	Dilutive effect of convertible debt	16,496		5,722		14,216		6,687
	Weighted average common and potential common shares outstanding	219,089		204,405		215,943		204,553
	Basic net income per common share	$	0.53	$	0.05	$	1.43	$	0.35
	Diluted net income per common share	$	0.48	$	0.05	$	1.31	$	0.33

Basis_of_Presentation_Details

Basis of Presentation (Details)	Dec. 31, 2013
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Percentage Of Outstanding Stock Of All Subsidiaries Owned	100.00%

Reclassification_of_Prior_Peri2

Reclassification of Prior Periods (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities	'	'
Amortization of premium on available-for-sale investments	$8,067	$10,304
Net cash provided by operating activities	473,223	331,482
Cash flows from investing activities	'	'
Purchases of available-for-sale investments	-950,560	-656,728
Net cash used in investing activities	-448,359	-931,111
As reported	'	'
Cash flows from operating activities	'	'
Amortization of premium on available-for-sale investments	'	0
Net cash provided by operating activities	'	321,178
Cash flows from investing activities	'	'
Purchases of available-for-sale investments	'	-646,424
Net cash used in investing activities	'	-920,807
Adjustment	'	'
Cash flows from operating activities	'	'
Amortization of premium on available-for-sale investments	'	10,304
Net cash provided by operating activities	'	10,304
Cash flows from investing activities	'	'
Purchases of available-for-sale investments	'	-10,304
Net cash used in investing activities	'	($10,304)

Business_Acquisitions_Details

Business Acquisitions (Details) (USD $)	9 Months Ended			0 Months Ended	9 Months Ended			9 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2013	Nov. 23, 2013	Dec. 31, 2013	Nov. 21, 2013	Nov. 20, 2013	Dec. 31, 2013	Mar. 31, 2013
				Eqcologic Acquisition [Member]	Eqcologic Acquisition [Member]	Eqcologic Acquisition [Member]	Eqcologic Acquisition [Member]	SMSC Acquisition [Member]	SMSC Acquisition [Member]
Business Acquisition [Line Items]	'	'	'	'	'	'	'	'	'
Business Acquisition, Effective Date of Acquisition	'	'	'	'	21-Nov-13	'	'	2-Aug-12	'
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage	'	'	'	'	'	'	18.30%	'	'
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	$2,438,000	$0	'	$2,438,000	'	'	'	'	'
Business Acquisition, Percentage of Voting Interests Acquired	'	'	'	'	'	81.70%	'	'	'
Business Combination, Consideration Transferred	'	'	'	'	'	9,000,000	'	'	'
Weighted average useful life of finite lived intangible assets (in years)	'	'	'	'	'8 years	'	'	'	'
Business Acquisition, Purchase Price Allocation [Abstract]	'	'	'	'	'	'	'	'	'
Cash and cash equivalents	'	'	'	'	'	'	'	180,925,000	180,925,000
Accounts recevable, net	'	'	'	'	'	'	'	58,441,000	58,441,000
Inventories	'	'	'	'	'	'	'	86,244,000	86,244,000
Prepaid expenses	'	'	'	'	'	'	'	5,617,000	5,617,000
Deferred tax assets	'	'	'	'	'	'	'	15,843,000	15,843,000
Other current assets	'	'	'	'	'	'	'	17,578,000	17,578,000
Property, plant and equipment, net	'	'	'	'	'	'	'	35,608,000	35,608,000
Long-term investments	'	'	'	'	'	'	'	24,275,000	24,275,000
Goodwill	'	'	'	'	'	6,400,000	'	165,592,000	169,065,000
Intangible assets, net	'	'	'	'	'	'	'	10,214,000	10,214,000
Purchased intangible assets	'	'	'	'	'	4,100,000	'	517,800,000	517,800,000
Other assets	'	'	'	'	'	'	'	3,835,000	3,835,000
Total assets acquired	'	'	'	'	'	'	'	1,121,972,000	1,125,445,000
Accounts payable	'	'	'	'	'	'	'	-28,035,000	-28,035,000
Accrued liabilities	'	'	'	'	'	'	'	-62,247,000	-62,038,000
Deferred income on shipments to distributors	'	'	'	'	'	'	'	-11,376,000	-11,376,000
Long-term income tax payable	'	'	'	'	'	'	'	-72,781,000	-72,781,000
Deferred tax liability	'	'	'	'	'	'	'	-16,682,000	-21,079,000
Other liabilities	'	'	'	'	'	'	'	-11,250,000	-10,535,000
Contingent consideration	0	'	19,100,000	'	'	'	'	'	'
Total liabilities assumed	'	'	'	'	'	'	'	-202,371,000	-205,844,000
Purchase price allocated	'	'	'	'	'	'	'	919,601,000	919,601,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]	'	'	'	'	'	'	'	'	'
Goodwill	'	'	'	'	'	'	'	-3,473,000	'
Total assets acquired	'	'	'	'	'	'	'	-3,473,000	'
Accrued liabilities	'	'	'	'	'	'	'	-209,000	'
Deferred tax liabilty	'	'	'	'	'	'	'	4,397,000	'
Other liabilities	'	'	'	'	'	'	'	-715,000	'
Total liabilities assumed	'	'	'	'	'	'	'	($3,473,000)	'

Special_Charges_Details

Special Charges (Details) (Unusual or Infrequent Item [Member], USD $)	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2012
			SMSC Acquisition [Member]	SMSC Acquisition [Member]	SST acquisition [Member]	SST acquisition [Member]
Unusual or Infrequent Item [Line Items]	'	'	'	'	'	'
Severance-Related, Office Closing Costs and Other Restructuring Costs	$0.80	$2.50	$2.60	$13.40	'	'
Legal settlement costs	'	'	'	'	$11.50	$11.50

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Segment reporting information [Line Items]	'	'	'	'
Net sales	$482,372	$416,047	$1,437,833	$1,151,479
Gross Profit	282,720	200,428	838,157	599,420
Semiconductor products [Member]	'	'	'	'
Segment reporting information [Line Items]	'	'	'	'
Net sales	458,298	394,709	1,366,415	1,089,738
Gross Profit	258,646	179,090	766,739	537,679
Technology licensing [Member]	'	'	'	'
Segment reporting information [Line Items]	'	'	'	'
Net sales	24,074	21,338	71,418	61,741
Gross Profit	$24,074	$21,338	$71,418	$61,741

Summary_of_Available_for_Sale_

Summary of Available for Sale (Details) (USD $)	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Summary of available-for-sale securities [Line Items]	'	'
Available-for-sale, adjusted cost	$1,660,297	$1,301,989
Available-for-sale, gross unrealized gains	3,042	6,189
Available-for-sale, gross unrealized losses	-7,112	-465
Available-for-sale, estimated fair value	1,656,227	1,307,713
Government agency bonds [Member]	'	'
Summary of available-for-sale securities [Line Items]	'	'
Available-for-sale, adjusted cost	741,492	558,116
Available-for-sale, gross unrealized gains	164	335
Available-for-sale, gross unrealized losses	-5,645	-298
Available-for-sale, estimated fair value	736,011	558,153
Municipal bonds [Member]	'	'
Summary of available-for-sale securities [Line Items]	'	'
Available-for-sale, adjusted cost	51,940	25,000
Available-for-sale, gross unrealized gains	20	146
Available-for-sale, gross unrealized losses	-209	-8
Available-for-sale, estimated fair value	51,751	25,138
Auction rate securities [Member]	'	'
Summary of available-for-sale securities [Line Items]	'	'
Available-for-sale, adjusted cost	9,827	33,459
Available-for-sale, gross unrealized gains	0	332
Available-for-sale, gross unrealized losses	0	0
Available-for-sale, estimated fair value	9,827	33,791
Corporate bonds and debt [Member]	'	'
Summary of available-for-sale securities [Line Items]	'	'
Available-for-sale, adjusted cost	857,038	680,144
Available-for-sale, gross unrealized gains	2,858	5,137
Available-for-sale, gross unrealized losses	-1,258	-159
Available-for-sale, estimated fair value	858,638	685,122
Equity Securities [Member]	'	'
Summary of available-for-sale securities [Line Items]	'	'
Available-for-sale, adjusted cost	'	5,270
Available-for-sale, gross unrealized gains	'	239
Available-for-sale, gross unrealized losses	'	0
Available-for-sale, estimated fair value	'	$5,509

Investments_AFS_Details

Investments AFS (Details) (USD $)	Dec. 31, 2013	Mar. 31, 2013
Investments [Abstract]	'	'
Amount of short-term investments	$932,302,000	$1,050,263,000
Amount of long-term investments	723,925,000	257,450,000
Amount of corporate debt securities with no contractual maturity excluded from estimated fair value of available-for-sale securities	$6,200,000	'

AFS_Debt_Maturities_Details

AFS, Debt Maturities (Details) (USD $)	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Schedule of available-for-sale securities, debt maturities [Line Items]	'	'
Available-for-sale, adjusted cost	$1,660,297	$1,301,989
Available-for-sale, gross unrealized gains	3,042	6,189
Available-for-sale, gross unrealized losses	-7,112	-465
Available-for-sale, estimated fair value	1,656,227	1,307,713
Total maturities [Member]	'	'
Schedule of available-for-sale securities, debt maturities [Line Items]	'	'
Available-for-sale, adjusted cost	1,654,107	'
Available-for-sale, gross unrealized gains	3,042	'
Available-for-sale, gross unrealized losses	-7,112	'
Available-for-sale, estimated fair value	1,650,037	'
Due in one year or less [Member]	'	'
Schedule of available-for-sale securities, debt maturities [Line Items]	'	'
Available-for-sale, adjusted cost	190,841	'
Available-for-sale, gross unrealized gains	721	'
Available-for-sale, gross unrealized losses	0	'
Available-for-sale, estimated fair value	191,562	'
Due after one year and through five years [Member]	'	'
Schedule of available-for-sale securities, debt maturities [Line Items]	'	'
Available-for-sale, adjusted cost	1,332,690	'
Available-for-sale, gross unrealized gains	2,321	'
Available-for-sale, gross unrealized losses	-2,223	'
Available-for-sale, estimated fair value	1,332,788	'
Due after five years and through ten years [Member]	'	'
Schedule of available-for-sale securities, debt maturities [Line Items]	'	'
Available-for-sale, adjusted cost	120,749	'
Available-for-sale, gross unrealized gains	0	'
Available-for-sale, gross unrealized losses	-4,889	'
Available-for-sale, estimated fair value	115,860	'
Due after ten years [Member]	'	'
Schedule of available-for-sale securities, debt maturities [Line Items]	'	'
Available-for-sale, adjusted cost	9,827	'
Available-for-sale, gross unrealized gains	0	'
Available-for-sale, gross unrealized losses	0	'
Available-for-sale, estimated fair value	$9,827	'

Measured_on_Recurring_Basis_De

Measured on Recurring Basis (Details) (USD $)

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2012

Mar. 31, 2012

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2013

Insurance Sector Auction Rate Securities [Member]

Insurance Sector Auction Rate Securities [Member]

Insurance Sector Auction Rate Securities [Member]

Insurance Sector Auction Rate Securities [Member]

Energy And Telecommunications Sector Insurance Sector Auction Rate Securities [Member]

Student Loan Auction Rate Securities [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Minimum [Member]

Maximum [Member]

Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Money Market Fund Deposits Fair Value Disclosure

$114,235,000

$100,878,000

'

'

'

'

'

'

'

'

$114,235,000

$100,878,000

$0

$0

$0

$0

Marketable Equity Securities Fair Value Disclosure

'

5,509,000

'

'

'

'

'

'

'

'

'

5,509,000

'

0

'

0

Corporate Bonds and Debt Fair Value Disclosure

858,638,000

685,122,000

'

'

'

'

'

'

'

'

0

0

852,448,000

678,932,000

6,190,000

6,190,000

Government Agency Bonds Fair Value Disclosure

736,011,000

558,153,000

'

'

'

'

'

'

'

'

0

0

736,011,000

558,153,000

0

0

Cash Deposit Accounts Fair Value Disclosure

260,865,000

427,456,000

'

'

'

'

'

'

'

'

0

0

260,865,000

427,456,000

0

0

Municipal Bonds Fair Value Disclosure

51,751,000

25,138,000

'

'

'

'

'

'

'

'

0

0

51,751,000

25,138,000

0

0

Auction Rate Securities Fair Value Disclosure

9,827,000

33,791,000

'

'

'

'

'

'

'

'

0

0

0

0

9,827,000

33,791,000

Contingent consideration

0

19,100,000

'

'

'

'

'

'

'

'

'

0

'

0

'

19,100,000

Fair Value, Assets and Liabilities, as Classified on the Condensed Consolidated Balance Sheets [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cash and cash equivalents

375,100,000

528,334,000

465,293,000

635,755,000

'

'

'

'

'

'

114,235,000

100,878,000

260,865,000

427,456,000

0

0

Short-term investments

932,302,000

1,050,263,000

'

'

'

'

'

'

'

'

0

0

932,302,000

1,050,263,000

0

0

Long-term investments

723,925,000

257,450,000

'

'

'

'

'

'

'

'

0

5,509,000

707,908,000

211,960,000

16,017,000

39,981,000

Total assets measured at fair value

2,031,327,000

1,836,047,000

'

'

'

'

'

'

'

'

114,235,000

106,387,000

1,901,075,000

1,689,679,000

16,017,000

39,981,000

Liabilities, Fair Value Disclosure

'

19,100,000

'

'

'

'

'

'

'

'

'

0

'

0

'

19,100,000

Available-for-sale Securities, Other Disclosure Items [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Value of auction rate securities for which recent auctions were unsuccessful

'

'

'

'

$9,800,000

$9,800,000

'

'

$5,300,000

$18,700,000

'

'

'

'

'

'

Discount rate

'

'

'

'

'

'

2.00%

2.50%

'

'

'

'

'

'

'

'

Liquidity risk premium (percentage)

'

'

'

'

'

'

9.10%

29.50%

'

'

'

'

'

'

'

'

Anticipated liquidity horizon

'

'

'

'

'

'

'7 years

'10 years

'

'

'

'

'

'

'

'

Unobservable_Input_Reconciliat

Unobservable Input Reconciliation Assets (Details) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Mar. 31, 2013
Fair value, assets measured on recurring basis, unobservable input reconciliation [Line Items]	'	'
Total Gains (Losses)	($599)	($4,481)
Auction rate securities [Member]	'	'
Fair value, assets measured on recurring basis, unobservable input reconciliation [Line Items]	'	'
Fair value, measurement with unobservable inputs reconciliation, beginning	33,791	10,246
Included in earnings	1,103	-412
Included in other comprehensive income (loss)	-332	332
Purchases, sales, issuances, and settlements, net	-24,735	-650
Acquisition-related	'	24,275
Fair value, measurement with unobservable inputs reconciliation, ending	9,827	33,791
Corporate Debt [Member]	'	'
Fair value, assets measured on recurring basis, unobservable input reconciliation [Line Items]	'	'
Fair value, measurement with unobservable inputs reconciliation, beginning	6,190	4,625
Included in earnings	0	0
Included in other comprehensive income (loss)	0	0
Purchases, sales, issuances, and settlements, net	0	1,565
Acquisition-related	'	0
Fair value, measurement with unobservable inputs reconciliation, ending	6,190	6,190
Total Gains (Losses) [Member]	'	'
Fair value, assets measured on recurring basis, unobservable input reconciliation [Line Items]	'	'
Included in earnings	-267	-4,813
Included in other comprehensive income (loss)	-332	332
Purchases, sales, issuances, and settlements, net	'	'
Acquisition-related	'	$0

Unobservable_Input_Reconciliat1

Unobservable Input Reconciliation Liabilities (Details) (Contingent consideration [Member], USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Mar. 31, 2013
Contingent consideration [Member]	'	'
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Fair value, measurements with unobservable inputs reconciliation, beginning	$19,100	$0
Included in earnings	-1,370	-4,400
Purchases, sales, issuances, and settlements, net	-20,470	'
Acquisition-related	'	14,700
Fair value, measurements with unobservable inputs reconciliation, ending	$0	$19,100

Assets_Not_Recorded_at_Fair_Va

Assets Not Recorded at Fair Value on a Recurring Basis (Details) (USD $)	3 Months Ended
	Dec. 31, 2012
Investments Not Recorded at Fair Value on a Recurring Basis [Abstract]	'
Cost-method Investments, Other than Temporary Impairment	$500,000

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Details) (USD $)	Dec. 31, 2013	Mar. 31, 2013
In Millions, unless otherwise specified
Fair Value Disclosures [Abstract]	'	'
Fair value of junior subordinated convertible debentures based on the trading price of the bonds	$1,987	$1,639

Accounts_Receivable_Details

Accounts Receivable (Details) (USD $)	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Receivable amounts	$226,934	$232,719
Less allowance for doubtful accounts	2,661	2,764
Accounts receivable, net	224,273	229,955
Trade Accounts Receivable [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Receivable amounts	224,832	230,469
Other Receivables [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Receivable amounts	$2,102	$2,250

Inventories_Details

Inventories (Details) (USD $)	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Inventory, Net [Abstract]	'	'
Raw materials	$9,555	$9,020
Work in process	187,822	181,750
Finished goods	77,252	51,564
Inventory, Net	$274,629	$242,334

Property_Plant_and_Equipment_D

Property, Plant and Equipment (Details) (USD $)	3 Months Ended		9 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2013
Property, Plant and Equipment [Line Items]	'	'	'	'	'
Property, plant, and equipment costs	$1,967,507,000	'	$1,967,507,000	'	$1,897,685,000
Accumulated depreciation	1,446,942,000	'	1,446,942,000	'	1,383,141,000
Property, plant and equipment, net	520,565,000	'	520,565,000	'	514,544,000
Depreciation expense	22,200,000	23,000,000	66,700,000	66,000,000	'
Land [Member]	'	'	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'	'	'
Property, plant, and equipment costs	55,601,000	'	55,601,000	'	47,102,000
Buildings and building improvements [Member]	'	'	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'	'	'
Property, plant, and equipment costs	407,520,000	'	407,520,000	'	396,611,000
Machinery and equipment [Member]	'	'	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'	'	'
Property, plant, and equipment costs	1,442,169,000	'	1,442,169,000	'	1,377,814,000
Projects in progress [Member]	'	'	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'	'	'
Property, plant, and equipment costs	$62,217,000	'	$62,217,000	'	$76,158,000

Accrued_Liabilities_Details

Accrued Liabilities (Details) (USD $)	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Liabilities, Current [Abstract]	'	'
Acquisition related contingent consideration	$0	$19,100
Other accrued expenses	96,176	108,008
Accrued Liabilities, Current	$96,176	$127,108

Income_tax_Details

Income tax (Details) (USD $)	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]	'	'	'
Effective Income Tax Rate	'	9.70%	34.10%
Tax Adjustments, Settlements, and Unusual Provisions	$6.20	'	'
Unrecognized Tax Benefits	179.2	179.2	'
Unrecognized Tax Benefits, Period Increase (Decrease)	'	$3.50	'

2125_Junior_subordinated_conve1

2.125% Junior subordinated convertible debentures (Details) (USD $)	3 Months Ended		9 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2013
Debt Instrument [Line Items]	'	'	'	'	'
Carrying value of debentures	$369,618,000	'	$369,618,000	'	$363,385,000
Amortization of Debt Discount (Premium)	2,300,000	2,100,000	6,682,000	6,106,000	'
Junior subordinated convertible debentures due 2037 [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Principal amount of junior subordinated convertible debentures	1,150,000,000	'	1,150,000,000	'	'
Interest rate of junior subordinated convertible debentures	2.13%	'	2.13%	'	'
Due date of junior subordinated convertible debentures	'	'	15-Dec-37	'	'
Conversion rate, in shares, of junior subordinated convertible debt (in shares per $1,000)	'	'	29.2783	'	'
Principal amount of junior subordinated convertible debentures used as conversion unit	'	'	1,000	'	'
Convertible Debt Instrument Initial Conversion Price Per Share	$34.16	'	$34.16	'	'
Debt Instrument, Convertible, Conversion Ratio	'	'	38.3572	'	'
Debt Instrument, Convertible, Conversion Price	$26.07	'	$26.07	'	'
Carrying value of equity component of the debentures that were bifurcated into a liability and equity component	822,400,000	'	822,400,000	'	822,400,000
Estimated fair value of liability component of debentures at issuance date	327,600,000	'	327,600,000	'	'
Debt discount of estimated fair value of liability component of debentures	822,400,000	'	822,400,000	'	'
Amount of unamortized debt discount of debentures	779,500,000	'	779,500,000	'	786,200,000
Remaining period, in years, over which unamortized debt discount will be recognized as non-cash interest expense (in years)	'	'	'24 years	'	'
Recognized amount of interest expense related to debentures	$6,100,000	$6,100,000	$18,300,000	$18,300,000	'

Credit_facility_Details

Credit facility (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Jun. 27, 2013

Dec. 31, 2013

Jun. 27, 2013

Dec. 31, 2013

Jun. 27, 2013

Jun. 27, 2013

Jun. 27, 2013

Dec. 31, 2013

Jun. 27, 2013

Jun. 27, 2013

Jun. 27, 2013

Jun. 27, 2013

Jun. 27, 2013

Jun. 27, 2013

Dec. 31, 2013

Jun. 27, 2013

Dec. 31, 2013

Jun. 27, 2013

Dec. 31, 2012

Dec. 31, 2012

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit Agreement Maturity June 27, 2018 [Member]

Credit agreement Maturity August 12, 2016 [Member]

Credit agreement Maturity August 12, 2016 [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit Facility Foreign Currency Sublimit [Member]

Line of Credit Facility Letter of Credit Sublimit [Member]

Line of Credit Facility Swingline Loan Sublimit [Member]

Term loan [Member]

Term loan [Member]

Revolving credit facility [Member]

Revolving credit facility [Member]

Debt Instrument Interest Rate Option1 [Member]

Debt Instrument Interest Rate Option1 [Member]

Debt Instrument Interest Rate Option1 [Member]

Debt Instrument Interest Rate Option1 [Member]

Debt Instrument Interest Rate Option 2 [Member]

Debt Instrument Interest Rate Option 2 [Member]

Debt Instrument Interest Rate Option 2 [Member]

Debt Instrument Interest Rate Option 2 [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Line of Credit Facility [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Initiation date

'

'

'

'

'

27-Jun-13

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit agreement

'

'

'

'

'

'

$2,000,000,000

'

'

'

'

'

'

'

'

'

'

$125,000,000

$35,000,000

$25,000,000

'

$350,000,000

'

$1,650,000,000

'

'

Borrowings outstanding under the Credit Agreement

'

'

'

'

650,000,000

650,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

350,000,000

'

300,000,000

'

'

'

Maturity Date

'

'

'

'

'

27-Jun-18

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Increase option amount

'

'

'

'

'

'

300,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt discount

'

'

'

'

1,200,000

1,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Spread on variable rate (percentage)

'

'

'

'

'

'

'

'

'

'

'

0.25%

1.25%

'

'

1.25%

2.25%

'

'

'

'

'

'

'

'

'

Description of variable rate basis

'

'

'

'

'

'

'

'

'

'the highest of JPMorgan Chase Bank, N.A.'s prime rate, the federal funds rate plus a margin equal to 0.50% and the adjusted LIBOR rate for a 1-month interest period plus a margin equal to 1.00%

'

'

'

'adjusted LIBOR rate (based on one, two, three, or six-month interest periods)

'

'

'

'

'

'

'

'

'

'

'

'

Additional basis on variable rate base (percentage)

'

'

'

'

'

'

'

'

'

'

0.50%

'

'

'

1.00%

'

'

'

'

'

'

'

'

'

'

'

Period for leverage ratio to determine interest rate spread

'

'

'

'

'

'

'

'preceding four fiscal quarter period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest expense

$12,545,000

$11,077,000

$36,755,000

$30,983,000

$4,100,000

$11,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$3,100,000

$6,100,000

Interest rate spread on overdue principal in event of default (percentage)

'

'

'

'

'

'

'

'

2.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate spread on overdue amounts in event of default (percentage)

'

'

'

'

'

'

'

'

2.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Contingencies_Details

Contingencies (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2013	Apr. 08, 2010
In Millions, unless otherwise specified	SST acquisition [Member]	SST acquisition [Member]	SST acquisition [Member]	Indemnification agreement [Member]	Pending Litigation [Member]
		Unusual or Infrequent Item [Member]	Unusual or Infrequent Item [Member]		SST acquisition [Member]
Loss contingencies [Line Items]	'	'	'	'	'
Loss contingencies, estimate of possible loss	'	'	'	$121	$13
Legal settlement costs	'	11.5	11.5	'	'
Contingent liabilities outstanding	$5.70	'	'	'	'

Derivative_Instruments_Details

Derivative Instruments (Details) (USD $)	9 Months Ended
	Dec. 31, 2013	Mar. 31, 2013
Derivative [Line Items]	'	'
Percentage Of Company Sales Denominated In Us Dollars	99.00%	'
Notional Amount of Foreign Currency Derivatives	'	$6,000,000

Comprehensive_Income_Schedule_

Comprehensive Income (Schedule of Changes in the Components of AOCI) (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
Changes in the components of AOCI	'
Balance at March 31, 2013	$6,935
Other comprehensive loss before reclassifications	-8,011
Amounts reclassified from accumulated other comprehensive income (loss)	-1,503
Net other comprehensive loss	-9,514
Balance at December 31, 2013	-2,579
Unrealized holding gains (losses) on available-for-sale securities	'
Changes in the components of AOCI	'
Balance at March 31, 2013	5,444
Other comprehensive loss before reclassifications	-8,011
Amounts reclassified from accumulated other comprehensive income (loss)	-1,503
Net other comprehensive loss	-9,514
Balance at December 31, 2013	-4,070
Minimum pension liability	'
Changes in the components of AOCI	'
Balance at March 31, 2013	52
Other comprehensive loss before reclassifications	0
Amounts reclassified from accumulated other comprehensive income (loss)	0
Net other comprehensive loss	0
Balance at December 31, 2013	52
Foreign Currency	'
Changes in the components of AOCI	'
Balance at March 31, 2013	1,439
Other comprehensive loss before reclassifications	0
Amounts reclassified from accumulated other comprehensive income (loss)	0
Net other comprehensive loss	0
Balance at December 31, 2013	$1,439

Comprehensive_Income_Schedule_1

Comprehensive Income (Schedule of Reclassifications of Recognized Transactions out of AOCI) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Unrealized gains on available-for-sale securities	$3,824	($228)	$6,093	$311
Taxes	-7,187	481	-30,344	-34,976
Reclassification of realized transactions, net of taxes	105,401	10,173	283,786	67,699
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains on available-for-sale securities	'	'	'	'
Reclassification out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Unrealized gains on available-for-sale securities	113	14	2,279	235
Taxes	0	0	-776	-51
Reclassification of realized transactions, net of taxes	$113	$14	$1,503	$184

ShareBased_Compensation_Detail

Share-Based Compensation (Details) (USD $)	3 Months Ended				9 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2013		Dec. 31, 2012
Stock-based compensation expense [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	$12,209,000		$11,365,000		$36,874,000		$37,163,000
Inventory [Member]	'		'		'		'
Stock-based compensation expense [Line Items]	'		'		'		'
Amount of share-based compensation expense capitalized to inventory	1,900,000		1,800,000		5,700,000		5,300,000
Cost of Sales [Member]	'		'		'		'
Stock-based compensation expense [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	1,841,000	[1]	1,834,000	[1]	5,674,000	[1]	5,758,000	[1]
Research and development [Member]	'		'		'		'
Stock-based compensation expense [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	6,141,000		6,172,000		18,762,000		16,562,000
Selling, General and Administrative Expenses [Member]	'		'		'		'
Stock-based compensation expense [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	5,737,000		6,114,000		16,939,000		22,339,000
Pre-tax effect of share based compensation [Member]	'		'		'		'
Stock-based compensation expense [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	13,719,000		14,120,000		41,375,000		44,659,000
Income tax benefit [Member]	'		'		'		'
Stock-based compensation expense [Line Items]	'		'		'		'
Allocated Share-based Compensation Expense	$1,510,000		$2,755,000		$4,501,000		$7,496,000
[1]	During the three and nine months ended DecemberB 31, 2013, $1.9 million and $5.7 million, respectively, of share-based compensation expense was capitalized to inventory and $1.8 million and $5.7 million, respectively, of previously capitalized share-based compensation expenses in inventory was sold. During the three and nine months ended DecemberB 31, 2012, $1.8 million and $5.3 million, respectively, of share-based compensation expense was capitalized to inventory and $1.8 million and $5.8 million, respectively, of previously capitalized share-based compensation expense in inventory was sold.

Net_income_per_common_share_De

Net income per common share (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]	'	'	'	'
Net income	$105,401	$10,173	$283,786	$67,699
Weighted average common shares outstanding	198,759,000	194,958,000	197,845,000	194,157,000
Dilutive effect of stock options and RSUs	3,834,000	3,725,000	3,882,000	3,709,000
Dilutive effect of convertible debt	16,496,384	5,721,774	14,215,573	6,687,078
Weighted average common and potential common shares outstanding	219,089,000	204,405,000	215,943,000	204,553,000
Basic net income per common share	$0.53	$0.05	$1.43	$0.35
Diluted net income per common share	$0.48	$0.05	$1.31	$0.33
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$26.19	$27.21	$26.43	$27.51
Number of antidilutive option shares (in shares)	'	124,395	'	110,021

Dividends_Details

Dividends (Details) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended		0 Months Ended
	Dec. 05, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Jan. 30, 2014
						Subsequent Event [Member]
Dividends [Abstract]	'	'	'	'	'	'
Dividend per share paid during period	$0.35	'	'	$1.06	'	'
Dividends paid during period	$70,600,000	'	'	$210,322,000	$204,592,000	'
Subsequent Event [Line Items]	'	'	'	'	'	'
Dividends declared per common share	'	$0.35	$0.35	$1.06	$1.05	$0.36
Total amount of expected dividend payment	'	'	'	'	'	$70,700,000