Microchip Technology (MCHP) 10-Q 7 Feb 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	9 Months Ended
	Dec. 31, 2017	Jan. 31, 2018
DEI Information [Abstract]
Entity Registrant Name	MICROCHIP TECHNOLOGY INC
Entity Central Index Key	827,054
Current Fiscal Year End Date	--03-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		234,343,061

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
ASSETS
Cash and cash equivalents	$ 672,079	$ 908,684
Short-term investments	427,514	394,088
Accounts receivable, net	553,135	478,373
Inventories	487,065	417,202
Prepaid expenses	60,117	41,354
Assets held for sale	0	6,459
Other current assets	53,531	58,880
Total current assets	2,253,441	2,305,040
Property, plant and equipment, net	754,780	683,338
Long-term investments	885,392	107,457
Goodwill	2,299,009	2,299,009
Intangible assets, net	1,784,568	2,148,092
Long-term deferred tax assets	70,793	68,870
Other assets	75,810	75,075
Total assets	8,123,793	7,686,881
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	162,718	149,233
Accrued liabilities	258,409	212,450
Deferred income on shipments to distributors	335,705	292,815
Current portion of long-term debt	0	49,952
Total current liabilities	756,832	704,450
Long-term debt	3,039,623	2,900,524
Long-term income tax payable	694,777	184,945
Long-term deferred tax liability	208,823	409,045
Other long-term liabilities	238,663	217,206
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; 253,232,881 shares issued and 234,340,716 shares outstanding at December 31, 2017; 249,463,733 shares issued and 229,093,658 shares outstanding at March 31, 2017	234	229
Additional paid-in capital	2,556,274	2,537,344
Common stock held in treasury: 18,892,165 shares at December 31, 2017; 20,370,075 shares at March 31, 2017	(684,937)	(731,884)
Accumulated other comprehensive loss	(22,193)	(14,378)
Retained earnings	1,335,697	1,479,400
Total stockholders' equity	3,185,075	3,270,711
Total liabilities and stockholders' equity	$ 8,123,793	$ 7,686,881

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) - $ / shares	Dec. 31, 2017	Mar. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in USD per share)	$ 0.001	$ 0.001
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 value (in USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized	450,000,000	450,000,000
Common stock, shares issued	253,232,881	249,463,733
Common stock, shares outstanding	234,340,716	229,093,658
Common stock, shares held in treasury	18,892,165	20,370,075

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales		$ 994,205	$ 834,366	$ 2,978,485	$ 2,505,141
Cost of sales	[1]	387,146	369,107	1,172,893	1,280,771
Gross profit		607,059	465,259	1,805,592	1,224,370
Research and development	[1]	131,555	132,433	395,656	418,111
Selling, general and administrative	[1]	109,059	111,017	337,620	388,651
Amortization of acquired intangible assets		121,003	82,791	362,761	243,356
Special charges and other, net		196	20,944	17,312	52,522
Operating expenses		361,813	347,185	1,113,349	1,102,640
Operating income		245,246	118,074	692,243	121,730
Losses on equity method investment		(56)	(55)	(167)	(167)
Other income (expense):
Interest income		6,306	501	14,441	1,765
Interest expense		(49,744)	(35,143)	(148,693)	(104,685)
Loss on settlement of convertible debt		(2,140)	0	(15,966)	0
Other (loss) income, net		(2,962)	121	7,233	(658)
Income before income taxes		196,650	83,498	549,091	17,985
Income tax provision (benefit)		447,736	(23,837)	440,434	(15,699)
Net (loss) income from continuing operations		(251,086)	107,335	108,657	33,684
Loss from discontinued operations		0	(191)	0	(7,514)
Income tax benefit		0	(31)	0	(1,561)
Net loss from discontinued operations		0	(160)	0	(5,953)
Net (loss) income		$ (251,086)	$ 107,175	$ 108,657	$ 27,731
Basic net (loss) income per common share
Basic net income (loss) from continuing operations, per common share (in USD per share)		$ (1.07)	$ 0.50	$ 0.47	$ 0.16
Basic net loss from discontinued operations, per common share (in USD per share)		0	0	0	(0.03)
Basic net income (loss) attributable to Microchip Technology, per common share (in USD per share)		(1.07)	0.50	0.47	0.13
Diluted net (loss) income per common share
Diluted net income (loss) from continuing operations, per common share (in USD per share)		(1.07)	0.46	0.44	0.14
Diluted net loss from discontinued operations, per common share (in USD per share)		0	0	0	(0.02)
Diluted net income (loss) attributable to Microchip Technology, per common share (in USD per share)		(1.07)	0.46	0.44	0.12
Dividends declared per common share (in USD per share)		$ 0.3625	$ 0.3605	$ 1.0860	$ 1.0800
Basic common shares outstanding		234,106	216,210	232,278	215,360
Diluted common shares outstanding		234,106	235,424	248,024	233,351
[1]	Includes share-based compensation expense as follows:Cost of sales 3,494 3,468 10,587 15,465 Research and development 10,921 9,881 31,797 37,569 Selling, general and administrative 9,588 8,771 27,637 53,055

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (PARENTHETICAL) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 24,003	$ 22,120	$ 70,021	$ 106,089
Cost of Sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	3,494	3,468	10,587	15,465
Research and Development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	10,921	9,881	31,797	37,569
Selling General And Administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 9,588	$ 8,771	$ 27,637	$ 53,055

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (251,086)	$ 107,175	$ 108,657	$ 27,731
Available-for-sale securities:
Unrealized holding losses, net of tax effect	(5,807)	(254)	(6,161)	(1,983)
Reclassification of realized transactions, net of tax effect	0	1,433	0	1,522
Defined benefit plans:
Actuarial gains (losses) related to defined benefit pension plans, net of tax benefit (provision) of $2,017, ($2,539), $3,402 and $1,206, respectively	1,212	6,998	(2,284)	(1,332)
Reclassification of realized transactions, net of tax effect	214	0	630	0
Change in net foreign currency translation adjustment	0	(3,109)	0	(5,678)
Other comprehensive (loss) income, net of tax effect	(4,381)	5,068	(7,815)	(7,471)
Comprehensive (loss) income	$ (255,467)	$ 112,243	$ 100,842	$ 20,260

CONDENSED CONSOLIDATED STATEME7

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (PARENTHETICAL) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Actuarial gains (losses) related to defined benefit pension plans, tax benefit (provision)	$ 2,017	$ (2,539)	$ 3,402	$ 1,206

CONDENSED CONSOLIDATED STATEME8

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands		9 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income		$ 108,657	$ 27,731
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		459,032	340,925
Deferred income taxes		67,555	(52,215)
Share-based compensation expense related to equity incentive plans		70,021	106,089
Loss on settlement of convertible debt		15,966	0
Amortization of debt discount on convertible debt		79,017	36,907
Amortization of debt issuance costs		4,952	3,182
Losses on equity method investments		167	167
Gains on sale of assets		(5,421)	(78)
Losses on write-down of fixed assets		60	1,278
Impairment of intangible assets		252	10,226
Realized losses on available-for-sale investment		0	89
Realized gains on equity method investment		0	(468)
Impairment of available-for-sale investment		0	1,433
Amortization of premium on available-for-sale investments		531	5
Changes in operating assets and liabilities, excluding impact of acquisitions:
Increase in accounts receivable		(74,762)	(43,551)
(Increase) decrease in inventories		(70,183)	220,674
Increase in deferred income on shipments to distributors		42,890	110,827
Increase (decrease) in accounts payable and accrued liabilities		41,782	(22,261)
Change in other assets and liabilities		15,663	(18,780)
Change in income tax payable		303,903	5,364
Operating cash flows related to discontinued operations		0	9,348
Net cash provided by operating activities		1,060,082	736,892
Cash flows from investing activities:
Purchases of available-for-sale investments		(1,338,140)	(35,147)
Maturities of available-for-sale investments		520,086	350
Sales of available-for-sale investments		0	470,215
Sale of equity method investment		0	468
Acquisition of Atmel, net of cash acquired		0	(2,747,516)
Investments in other assets		(5,384)	(9,597)
Proceeds from sale of assets		10,289	23,069
Capital expenditures		(148,412)	(52,338)
Net cash used in investing activities		(961,561)	(2,350,496)
Cash flows from financing activities:
Payments on settlement of convertible debt	[1]	(73,421)	0
Repayments of revolving loan under credit facility	[1]	(187,000)	(1,078,500)
Proceeds from borrowings on revolving loan under credit facility	[1]	187,000	1,517,000
Deferred financing costs	[1]	(1,208)	0
Payment of cash dividends	[1]	(252,360)	(232,847)
Proceeds from sale of common stock	[1]	26,576	28,893
Tax payments related to shares withheld for vested restricted stock units	[1]	(34,126)	(48,161)
Capital lease payments	[1]	(587)	(587)
Net cash (used in) provided by financing activities	[1]	(335,126)	185,798
Effect of foreign exchange rate changes on cash and cash equivalents		0	(1,007)
Net decrease in cash and cash equivalents		(236,605)	(1,428,813)
Cash and cash equivalents at beginning of period		908,684	2,092,751
Cash and cash equivalents at end of period		$ 672,079	$ 663,938
[1]	During the nine months ended December 31, 2017, the Company issued $111.3 million principal amount of 2017 Junior Notes and 3.2 million shares of common stock in exchange for $111.3 million principal amount of 2007 Junior Notes. Refer to Note 13 Debt and Credit Facility for further discussion.

CONDENSED CONSOLIDATED STATEME9

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (PARENTHETICAL) - Long-term Debt shares in Millions, $ in Millions	9 Months Ended
	Dec. 31, 2017USD ($)shares
2017 Junior Subordinated Convertible Debt
2017 Junior Notes Issued	$ 111.3
2007 Junior Subordinated Convertible Debt
Stock issued during period, shares, exchange of convertible securities | shares	3.2
2007 Junior Notes Exchanged	$ 111.3

Basis of Presentation (Notes)

Basis of Presentation (Notes)	9 Months Ended
	Dec. 31, 2017
Basis of Presentation [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of Microchip Technology Incorporated and its majority-owned and controlled subsidiaries (the Company). All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (US GAAP), 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, 2017 . The results of operations for the nine months ended December 31, 2017 are not necessarily indicative of the results that may be expected for the fiscal year ending March 31, 2018 or for any other period.

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements (Notes)	9 Months Ended
	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements Recently Adopted Accounting Pronouncements During the three months ended June 30, 2017, the Company adopted ASU 2015-11- Simplifying the Measurement of Inventory. This standard requires that entities measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. ASU 2015-11 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2016 and is applied prospectively. The adoption of this standard did not have a material impact on the Company's financial statements. In March 2017, the Financial Accounting Standards Board (FASB) issued ASU 2017-07- Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . This standard improves the presentation of net periodic pension cost and net periodic postretirement benefit cost. The amendment will require the employer to report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost will be presented separately in the income statement from the service cost component outside of income from operations. The amendment is effective for fiscal years beginning after December 15, 2017. Early adoption is permitted at the beginning of an annual period (in the first interim period) for which financial statements have not yet been issued. During the three months ended June 30, 2017, the Company elected to early adopt ASU 2017-07 and the adoption of this standard did not have a material impact on its financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In August 2017, the FASB issued ASU 2017-12- Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities . The update expands an entity's ability to apply hedge accounting for nonfinancial and financial risk components and allows for a simplified approach for fair value hedging of interest rate risk. The update eliminates the need to separately measure and report hedge ineffectiveness and generally requires the entire change in fair value of a hedging instrument to be presented in the same income statement line as the hedged item. Additionally, the update simplifies the hedge documentation and effectiveness assessment requirements under the previous guidance. The effective date of this standard is for fiscal years beginning after December 15, 2018 and early adoption is permitted. Adoption will be applied through a cumulative-effect adjustment for cash flow and net investment hedges existing at the date of adoption and prospectively for presentation and disclosure. The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04- Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment , which simplifies the accounting for goodwill impairment. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The amendment is effective for annual periods and interim periods within those annual periods, beginning after December 15, 2019, and early adoption is permitted. The Company does not expect this standard to have an impact on its consolidated financial statements. In November 2016, the FASB issued ASU 2016-18- Statement of Cash Flows: Restricted Cash. This standard requires that the statement of cash flows explain the change during the period in total cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. The standard is to be applied using a retrospective transition method to each period presented. The Company does not expect this standard to have a material impact on its consolidated financial statements. In October 2016, the FASB issued ASU 2016-16- Intra-Entity Transfers of Assets Other Than Inventory . This standard addresses the recognition of current and deferred income taxes resulting from an intra-entity transfer of any asset other than inventory. Prior to the adoption of ASU 2016-16, a company will defer for financial reporting purposes the income tax expense resulting from an intra-entity asset transfer, including the taxes currently payable or paid. Upon adoption of ASU 2016-16, a company will recognize current and deferred income taxes that result from such transfers in the period in which they occur. ASU 2016-16 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017 and is applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements but expects to recognize its previously deferred tax related to intra-entity transfers upon adoption of ASU 2016-16 as of April 1, 2018 with a cumulative-effect reduction to retained earnings. In June 2016, the FASB issued ASU 2016-13- Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments. This standard requires entities to use a current lifetime expected credit loss methodology to measure impairments of certain financial assets. Using this methodology will result in earlier recognition of losses than under the current incurred loss approach, which requires waiting to recognize a loss until it is probable of having been incurred. The amendments in ASU 2016-13 broaden the information that an entity must consider in developing its expected credit loss estimate for assets measured either collectively or individually and can include forecasted information. There are other provisions within the standard affecting how impairments of other financial assets may be recorded and presented, as well as expanded disclosures. ASU 2016-13 is effective for interim and annual periods beginning after December 15, 2019, and permits early adoption, but not before December 15, 2018. The standard is to be applied using a modified retrospective approach. The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements. In February 2016, the FASB issued ASU 2016-02 -Leases . This standard requires lessees to recognize a lease liability and a right-of-use asset on the balance sheet and aligns many of the underlying principles of the new lessor model with those in Accounting Standards Codification Topic 606, Revenue from Contracts with Customers . ASU 2016-02 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2018, with early adoption permitted. The standard is to be applied using the modified retrospective approach to all periods presented. The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements. In January 2016, the FASB issued ASU 2016-01- Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities . This standard addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. ASU 2016-01 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. Early adoption is not permitted. The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements. In May 2014, the FASB issued ASU 2014-09 -Revenue from Contracts with Customers (Topic 606) , which will supersede nearly all existing revenue recognition guidance under US GAAP. In July 2015, the FASB issued ASU 2015-14- Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date , which delayed the effective date of the new standard by one year to December 15, 2017, for annual and interim reporting periods beginning after that date. In accordance with the delay, the new standard will be effective for the Company beginning no later than April 1, 2018. The standard's core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The new standard allows for the amendment to be applied either retrospectively to each prior reporting period presented or retrospectively as a cumulative-effect adjustment as of the date of adoption. In March 2016, the FASB issued ASU 2016-08 - Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU 2016-10 - Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which clarifies the implementation guidance on identifying performance obligations. In May 2016, the FASB issued ASU 2016-12 - Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients , which addresses implementation issues that were raised by stakeholders and discussed by the Revenue Recognition Transition Resource Group. As described in the Company's significant accounting policies, the Company currently defers the revenue and cost of sales on shipments to distributors until the distributor sells the product to their end customer. Upon adoption of ASU 2014-09, ASU 2015-14, ASU 2016-08, ASU 2016-10 and ASU 2016-12, the Company will no longer defer revenue until sale by the distributor to the end customer, but rather, will be required to estimate the effects of returns and allowances provided to distributors and record revenue at the time of sale to the distributor. After adoption, the effect of the new standard on the Company's future consolidated financial statements will depend on the relative percentage of sales through distributors; the level of and changes in the amount of inventory held by distributors; the individual products and product types held in inventory by distributors; and the Company's ability to accurately estimate pricing variability at the time of sale to the distributor. The Company will adopt the standard under the modified retrospective method.

Business Acquisitions (Notes)

Business Acquisitions (Notes)	9 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Business Acquisitions	Business Acquisitions Acquisition of Atmel On April 4, 2016, the Company acquired Atmel, a publicly traded company based in San Jose, California. The Company paid an aggregate of approximately $ 2.98 billion in cash and issued an aggregate of 10.1 million shares of its common stock to Atmel stockholders valued at $486.1 million based on the closing price of the Company's common stock on April 4, 2016 and incurred transaction and other fees of approximately $ 14.9 million . The total consideration transferred in the acquisition, including approximately $ 7.5 million of non-cash consideration for the exchange of certain share-based payment awards of Atmel for stock awards of the Company, was approximately $ 3.47 billion . In addition to the consideration transferred, the Company recognized in its consolidated financial statements $653.1 million in liabilities of Atmel consisting of debt, taxes payable and deferred, pension obligations, restructuring, and contingent and other liabilities. The Company financed the cash portion of the purchase price using approximately $ 2.04 billion of cash held by certain of its foreign subsidiaries and approximately $ 0.94 billion from additional borrowings under its existing credit agreement. As a result of the acquisition, Atmel became a wholly owned subsidiary of the Company. Atmel is a worldwide leader in the design and manufacture of microcontrollers, capacitive touch solutions, advanced logic, mixed-signal, nonvolatile memory and radio frequency components. The Company's primary reason for this acquisition was to expand the Company's range of solutions, products and capabilities by extending its served available market. The acquisition was accounted for under the acquisition method of accounting, with the Company identified as the acquirer, and the operating results of Atmel have been included in the Company's consolidated financial statements as of the closing date of the acquisition. Under the acquisition method of accounting, the aggregate amount of consideration paid by the Company was allocated to Atmel's net tangible assets and intangible assets based on their estimated fair values as of April 4, 2016. The excess of the purchase price over the value of the net tangible assets and intangible assets was recorded to goodwill. The factors contributing to the recognition of goodwill were based upon the Company's conclusion that there are strategic and synergistic benefits that are expected to be realized from the acquisition. The goodwill has been allocated to the Company's semiconductor products reporting segment. None of the goodwill related to the Atmel acquisition is deductible for tax purposes. The Company retained independent third-party appraisers to assist management in its valuation. The table below represents the allocation of the final purchase price to the net assets acquired based on their estimated fair values, as well as the associated estimated useful lives of the acquired intangible assets (amounts in thousands). Assets acquired Cash and cash equivalents $ 230,266 Accounts receivable 141,359 Inventories 335,163 Prepaid expenses and other current assets 28,360 Assets held for sale 32,006 Property, plant and equipment 129,884 Goodwill 1,286,371 Purchased intangible assets 1,888,392 Long-term deferred tax assets 46,700 Other assets 7,535 Total assets acquired 4,126,036 Liabilities assumed Accounts payable (55,686 ) Other current liabilities (120,955 ) Long-term line of credit (192,000 ) Deferred tax liabilities (27,552 ) Long-term income tax payable (115,177 ) Other long-term liabilities (141,688 ) Total liabilities assumed (653,058 ) Purchase price allocated $ 3,472,978 Purchased Intangible Assets Weighted Average Useful Life (in years) (in thousands) Core and developed technology 11 $ 1,074,987 In-process research and development — 140,700 Customer-related 6 630,600 Backlog 1 40,300 Other 5 1,805 Total purchased intangible assets $ 1,888,392 Purchased intangible assets include core and developed technology, in-process research and development, customer-related intangibles, acquisition-date backlog and other intangible assets. The estimated fair values of the core and developed technology and in-process research and development were determined based on the present value of the expected cash flows to be generated by the respective existing technology or future technology. The core and developed technology intangible assets are being amortized in a manner based on the expected cash flows used in the initial determination of fair value. In-process research and development is capitalized until such time as the related projects are completed or abandoned at which time the capitalized amounts will begin to be amortized or written off. Customer-related intangible assets consist of Atmel's contractual relationships and customer loyalty related to its distributor and end-customer relationships, and the fair values of the customer-related intangibles were determined based on Atmel's projected revenues. An analysis of expected attrition and revenue growth for existing customers was prepared from Atmel's historical customer information. Customer relationships are being amortized in a manner based on the estimated cash flows associated with the existing customers and anticipated retention rates. Backlog relates to the value of orders not yet shipped by Atmel at the acquisition date, and the fair values were based on the estimated profit associated with those orders. Backlog related assets had a one year useful life and were being amortized on a straight-line basis over that period. The total weighted average amortization period of intangible assets acquired as a result of the Atmel transaction is 9 years. Amortization expense associated with acquired intangible assets is not deductible for tax purposes. Thus, approximately $178.1 million was established as a net deferred tax liability for the future amortization of the intangible assets.

Discontinued Operations (Notes)

Discontinued Operations (Notes)	9 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Discontinued Operations Discontinued operations include the mobile touch operations that the Company acquired as part of its acquisition of Atmel. The mobile touch assets had been marketed for sale since the Company's acquisition of Atmel on April 4, 2016 based on management's decision that it was not a strategic fit for the Company's product portfolio. On November 10, 2016, the Company completed the sale of the mobile touch assets to Solomon Systech (Limited) International, a Hong Kong based semiconductor company. The transaction included the sale of certain semiconductor products, equipment, customer list, backlog, patents, and a license to certain other intellectual property and patents related to the Company's mobile touch product line. The Company also agreed to provide certain transition services to Solomon Systech, which were substantially complete as of March 31, 2017. For financial statement purposes, the results of operations for this discontinued business have been segregated from those of the continuing operations and are presented in the Company's condensed consolidated financial statements as discontinued operations. As the Company completed the sale of the mobile touch assets on November 10, 2016, there are no discontinued operations for the three and nine months ended December 31, 2017 . The results of discontinued operations for the three and nine months ended December 31, 2016 are as follows (amounts in thousands): December 31, 2016 Three Months Ended Nine Months Ended Net sales $ 923 $ 18,334 Cost of sales 478 15,841 Operating expenses 1,279 10,650 Gain on Sale 643 643 Income tax benefit (31 ) (1,561 ) Net loss from discontinued operations $ (160 ) $ (5,953 )

Special Charges and Other, Net

Special Charges and Other, Net (Notes)	9 Months Ended
	Dec. 31, 2017
Other Nonrecurring (Income) Expense [Abstract]
Special Charges and Other, Net	Special Charges and Other, Net The following table summarizes activity included in the "special charges and other, net" caption on the Company's condensed consolidated statements of operations (amounts in thousands): Three Months Ended Nine Months Ended December 31, December 31, 2017 2016 2017 2016 Restructuring Employee separation costs $ 90 $ 6,525 $ 1,477 $ 35,346 Gain on sale of assets — — (4,447 ) — Impairment charges 99 8,084 199 10,045 Contract exit costs (97 ) 4,954 20,057 5,294 Other 104 1,381 26 1,837 Total $ 196 $ 20,944 $ 17,312 $ 52,522 The Company continuously evaluates its existing operations in an attempt to identify and realize cost savings opportunities and operational efficiencies. This same approach is applied to businesses that are acquired by the Company and often the operating models of acquired companies are not as efficient as the Company's operating model which enables the Company to realize significant savings and efficiencies. As a result, following an acquisition, the Company will from time to time incur restructuring expenses; however, the Company is often not able to estimate the timing or amount of such costs in advance of the period in which they occur. The primary reason for this is that the Company regularly reviews and evaluates each position, contract and expense against the Company's strategic objectives, long-term operating targets and other operational priorities. Decisions related to restructuring activities are made on a "rolling basis" during the course of the integration of an acquisition whereby department managers, executives and other leaders work together to evaluate each of these expenses and make recommendations. As a result of this approach, at the time of an acquisition, the Company is not able to estimate the total amount of expected employee separation or exit costs that it will incur in connection with its restructuring activities. The Company's restructuring expenses during fiscal 2017 were related to the Company's recent business combinations, including the acquisitions of Atmel and Micrel, and resulted from workforce, property and other operating expense rationalizations as well as combining product roadmaps and manufacturing operations. These expenses were for employee separation costs, contract exit costs, other operating expenses and intangible asset impairment losses. At March 31, 2017, these activities were substantially complete; however, the Company may continue to incur additional costs in the future as additional synergies or operational efficiencies are identified. The Company is not able to estimate the amount of such future expenses, if any, at this time. All of the Company's restructuring activities occurred in its semiconductor products segment. The Company incurred $52.6 million in costs since the start of fiscal 2015 in connection with employee separation activities, of which $0.1 million and $1.5 million was incurred during the three and nine months ended December 31, 2017 , respectively, and $6.5 million and $35.3 million was incurred during the during the three and nine months ended December 31, 2016, respectively. These employee separation activities are now substantially complete and any future amounts are not expected to be material. The Company has incurred $64.8 million in costs in connection with contract exit activities since the start of fiscal 2015 which includes income of $0.1 million and costs of $20.1 million for the three and nine months ended December 31, 2017 , respectively, and $5.0 million and $5.3 million was incurred for the three and nine months ended December 31, 2016, respectively. These acquisition-related contract exit activities are now substantially complete and any future amounts are not expected to be material. In the three months ended September 30, 2017, the Company recognized a $19.5 million charge for fees associated with transitioning from the public utility provider in Oregon to a lower cost direct access provider. The fee will be paid monthly starting in calendar year 2018 and will depend on the amount of actual energy consumed by the Company's wafer fabrication facility in Oregon over the next five years. In connection with the transition to a direct access provider, the Company signed a ten -year supply agreement to purchase monthly amounts of energy that are less than the current average usage and priced on a per mega watt hour published index rate in effect at those future dates. In the three months ended June 30, 2017, the Company completed the sale of an asset it acquired as part of its acquisition of Micrel for proceeds of $10.0 million and the gain of $4.4 million is included in the gain on sale of assets in the above table. As of March 31, 2017, these assets consisting of property, plant and equipment were presented as held for sale in the Company's condensed consolidated financial statements. The impairment losses in the nine months ended December 31, 2016 were recognized as a result of changes in the combined product roadmaps after the acquisition of Atmel that affected the use and life of these assets. The following is a roll forward of accrued restructuring charges from April 1, 2017 to December 31, 2017 (amounts in thousands): Employee Separation Costs Exit Costs Total Balance at April 1, 2017 - Restructuring Accrual $ 5,474 $ 34,751 $ 40,225 Charges 1,477 20,057 21,534 Payments (4,755 ) (7,090 ) (11,845 ) Non-cash - Other (287 ) 869 582 Foreign exchange gains 272 — 272 Balance at December 31, 2017 - Restructuring Accrual $ 2,181 $ 48,587 $ 50,768 Current $ 14,042 Non-current 36,726 Total $ 50,768 The restructuring liability of $50.8 million is included in accrued liabilities and other long-term liabilities on the Company's condensed consolidated balance sheet as of December 31, 2017 .

Segment Information (Notes)

Segment Information (Notes)	9 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Information	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, 2017 (amounts in thousands): Three Months Ended Nine Months Ended December 31, 2017 December 31, 2017 Net Sales Gross Profit Net Sales Gross Profit Semiconductor products $ 966,678 $ 579,532 $ 2,900,145 $ 1,727,252 Technology licensing 27,527 27,527 78,340 78,340 Total $ 994,205 $ 607,059 $ 2,978,485 $ 1,805,592 The following table represents net sales and gross profit for each segment for the three and nine months ended December 31, 2016 (amounts in thousands): Three Months Ended Nine Months Ended December 31, 2016 December 31, 2016 Net Sales Gross Profit Net Sales Gross Profit Semiconductor products $ 810,532 $ 441,425 $ 2,437,049 $ 1,156,278 Technology licensing 23,834 23,834 68,092 68,092 Total $ 834,366 $ 465,259 $ 2,505,141 $ 1,224,370

Investments (Notes)

Investments (Notes)	9 Months Ended
	Dec. 31, 2017
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, 2017 (amounts in thousands): Available-for-sale Securities Adjusted Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Government agency bonds $ 815,940 $ — $ (5,809 ) $ 810,131 Municipal bonds - taxable 10,000 — (57 ) 9,943 Corporate bonds and debt 491,851 — (1,484 ) 490,367 Marketable equity securities 707 1,758 — 2,465 Total $ 1,318,498 $ 1,758 $ (7,350 ) $ 1,312,906 The following is a summary of available-for-sale securities at March 31, 2017 (amounts in thousands): Available-for-sale Securities Adjusted Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Government agency bonds $ 227,089 $ 3 $ (227 ) $ 226,865 Municipal bonds - tax-exempt 55,289 — (10 ) 55,279 Municipal bonds - taxable 10,000 43 — 10,043 Corporate bonds and debt 207,888 53 (169 ) 207,772 Marketable equity securities 707 879 — 1,586 Total $ 500,973 $ 978 $ (406 ) $ 501,545 At December 31, 2017 , the Company's available-for-sale securities are presented on the condensed consolidated balance sheets as short-term investments of $427.5 million and long-term investments of $885.4 million . At March 31, 2017 , the Company's available-for-sale securities are presented on the condensed consolidated balance sheets as short-term investments of $394.1 million and long-term investments of $107.5 million . The Company had no proceeds from sales of available-for-sale investments during the nine months ended December 31, 2017 . The Company sold available-for-sale investments for proceeds of $470.2 million during the nine months ended December 31, 2016 to finance a portion of the purchase price of its Atmel acquisition which closed on April 4, 2016. No available-for-sale investments were sold during the three months ended December 31, 2016 . The Company had no material realized gains from the sale of available-for-sale securities during the three and nine months ended December 31, 2017 and 2016. The Company determines the cost of available-for-sale debt securities sold on a first-in first-out (FIFO) basis at the individual security level for sales from multiple lots. For sales of marketable equity securities, the Company uses an average cost basis at the individual security level. Gains and losses recognized in earnings are credited or charged to other income (expense) on the consolidated statements of operations. The following tables show all investments in an unrealized loss position for which an other-than-temporary impairment has not been recognized and the related gross unrealized losses and fair value, aggregated by investment category and the length of time that the individual securities have been in a continuous unrealized loss position (amounts in thousands): December 31, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Government agency bonds $ 790,325 $ (5,615 ) $ 19,806 $ (194 ) $ 810,131 $ (5,809 ) Municipal bonds - taxable 9,943 (57 ) — — 9,943 (57 ) Corporate bonds and debt 447,061 (1,484 ) — — 447,061 (1,484 ) Total $ 1,247,329 $ (7,156 ) $ 19,806 $ (194 ) $ 1,267,135 $ (7,350 ) March 31, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Government agency bonds $ 196,875 $ (227 ) $ — $ — $ 196,875 $ (227 ) Municipal bonds - tax exempt 55,279 (10 ) — — 55,279 (10 ) Corporate bonds and debt 132,820 (169 ) — — 132,820 (169 ) Total $ 384,974 $ (406 ) $ — $ — $ 384,974 $ (406 ) 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, 2017 and the Company's intent is to hold these investments until these assets are no longer impaired. The amortized cost and estimated fair value of the available-for-sale securities at December 31, 2017 , by contractual maturity, excluding marketable equity securities of $2.5 million , which have 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 Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available-for-sale Due in one year or less $ 425,436 $ — $ (387 ) $ 425,049 Due after one year and through five years 892,355 — (6,963 ) 885,392 Due after five years and through ten years — — — — Total $ 1,317,791 $ — $ (7,350 ) $ 1,310,441

Fair Value Measurements (Notes)

Fair Value Measurements (Notes)	9 Months Ended
	Dec. 31, 2017
Fair Value, Assets, Liabilities and Stockholders' Equity 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 mutual funds. 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 Measured at Fair Value on a Recurring Basis Assets measured at fair value on a recurring basis at December 31, 2017 are as follows (amounts in thousands): Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Total Balance Assets Cash and cash equivalents: Money market mutual funds $ 108,204 $ — $ 108,204 Deposit accounts — 563,875 563,875 Short-term investments: Marketable equity securities 2,465 — 2,465 Corporate bonds and debt — 288,224 288,224 Government agency bonds — 136,825 136,825 Long-term investments: Corporate bonds and debt — 202,143 202,143 Government agency bonds — 673,306 673,306 Municipal bonds - taxable — 9,943 9,943 Total assets measured at fair value $ 110,669 $ 1,874,316 $ 1,984,985 Assets measured at fair value on a recurring basis at March 31, 2017 are as follows (amounts in thousands): Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Total Balance Assets Cash and cash equivalents: Money market mutual funds $ 343,815 $ — $ 343,815 Deposit accounts — 564,869 564,869 Short-term investments: Marketable equity securities 1,586 — 1,586 Corporate bonds and debt — 165,207 165,207 Government agency bonds — 161,973 161,973 Municipal bonds - tax-exempt — 55,279 55,279 Municipal bonds - taxable — 10,043 10,043 Long-term investments: Corporate bonds and debt — 42,565 42,565 Government agency bonds — 64,892 64,892 Total assets measured at fair value $ 345,401 $ 1,064,828 $ 1,410,229 There were no transfers between Level 1 and Level 2 during the three and nine months ended December 31, 2017 or the fiscal year ended March 31, 2017 . There were no assets measured at fair value on a recurring basis classified as Level 3 at December 31, 2017 or March 31, 2017 . Assets and Liabilities Measured and Recorded at Fair Value on a Non-Recurring Basis The Company's non-marketable equity, cost method investments, certain acquired liabilities and non-financial assets, such as intangible assets, assets held for sale and property, plant and equipment, are recorded at fair value on a non-recurring basis. These assets are subject to fair value adjustments in certain circumstances, for example, when there is evidence of impairment. The Company's non-marketable and cost method investments are monitored on a quarterly basis for impairment charges. The fair values of these investments have been determined as Level 3 fair value measurements because the valuations use unobservable inputs that require management's judgment due to the absence of quoted market prices. There were no impairment charges recognized on these investments during each of the three and nine -month periods ended December 31, 2017 and December 31, 2016 . These investments are included in other assets on the condensed consolidated balance sheet. The fair value measurements related to the Company's non-financial assets, such as intangible assets, assets held for sale and property, plant and equipment are based on available market prices at the measurement date based on transactions of similar assets and third-party independent appraisals, less costs to sell where appropriate. The Company classifies these measurements as Level 2.

Fair Value of Financial Instrum

Fair Value of Financial Instruments (Notes)	9 Months Ended
	Dec. 31, 2017
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, 2017 based upon unobservable inputs. The fair values of these investments have been determined as Level 3 fair value measurements. The carrying amount of accounts receivable, accounts payable and accrued liabilities approximates fair value due to the short-term maturity of the amounts and are considered Level 2 in the fair value hierarchy. Fair Value of Subordinated Convertible Debt The Company measures the fair value of its senior and junior subordinated convertible debt for disclosure purposes. These fair values are based on observable market prices for this debt, which is traded in less active markets and are therefore classified as a Level 2 fair value measurement. The following table shows the carrying amounts and fair values of the Company's senior and junior subordinated convertible debt as of December 31, 2017 and March 31, 2017 (amounts in thousands). As of December 31, 2017 and March 31, 2017 , the carrying amounts of the Company's senior and junior subordinated convertible debt have been reduced by debt issuance costs of $35.2 million and $38.3 million , respectively. December 31, 2017 March 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value 2017 Senior Debt $ 1,424,169 $ 2,436,742 $ 1,384,914 $ 2,106,225 2015 Senior Debt $ 1,297,605 $ 2,952,993 $ 1,261,787 $ 2,481,708 2017 Junior Debt $ 324,528 $ 814,329 $ 262,298 $ 586,609 2007 Junior Debt $ — $ — $ 49,952 $ 445,142

Other Financial Statements Deta

Other Financial Statements Details (Notes)	9 Months Ended
	Dec. 31, 2017
Accounts Receivable, Net [Abstract]
Other Financial Statements Details	Other Financial Statement Details Accounts Receivable Accounts receivable consists of the following (amounts in thousands): December 31, 2017 March 31, 2017 Trade accounts receivable $ 547,572 $ 473,238 Other 7,682 7,219 Total accounts receivable, gross 555,254 480,457 Less allowance for doubtful accounts 2,119 2,084 Total accounts receivable, net $ 553,135 $ 478,373 Inventories The components of inventories consist of the following (amounts in thousands): December 31, 2017 March 31, 2017 Raw materials $ 22,488 $ 14,430 Work in process 309,811 268,281 Finished goods 154,766 134,491 Total inventories $ 487,065 $ 417,202 Inventories are valued at the lower of cost and net realizable value 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 Property, plant and equipment consists of the following (amounts in thousands): December 31, 2017 March 31, 2017 Land $ 73,447 $ 73,447 Building and building improvements 506,037 499,668 Machinery and equipment 1,911,200 1,774,920 Projects in process 115,006 104,318 Total property, plant and equipment, gross 2,605,690 2,452,353 Less accumulated depreciation and amortization 1,850,910 1,769,015 Total property, plant and equipment, net $ 754,780 $ 683,338 Depreciation expense attributed to property, plant and equipment was $32.0 million and $90.9 million for the three and nine months ended December 31, 2017 , respectively, compared to $29.7 million and $90.3 million for the three and nine months ended December 31, 2016 , respectively.

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Notes)	9 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	Intangible Assets and Goodwill Intangible assets consist of the following (amounts in thousands): December 31, 2017 Gross Amount Accumulated Amortization Net Amount Core and developed technology $ 1,936,956 $ (587,415 ) $ 1,349,541 Customer-related 716,945 (312,851 ) 404,094 Trademarks and trade names 11,700 (11,185 ) 515 In-process research and development 29,379 — 29,379 Distribution rights 5,578 (5,379 ) 199 Other 1,449 (609 ) 840 Total $ 2,702,007 $ (917,439 ) $ 1,784,568 March 31, 2017 Gross Amount Accumulated Amortization Net Amount Core and developed technology $ 1,932,329 $ (419,468 ) $ 1,512,861 Customer-related 716,945 (123,616 ) 593,329 Trademarks and trade names 11,700 (9,636 ) 2,064 In-process research and development 38,511 — 38,511 Distribution rights 5,578 (5,346 ) 232 Other 1,449 (354 ) 1,095 Total $ 2,706,512 $ (558,420 ) $ 2,148,092 The Company amortizes intangible assets over their expected useful lives, which range between 1 and 15 years. During the nine months ended December 31, 2017 , $ 8.9 million of in-process research and development reached technological feasibility and was reclassified as core and developed technology and began being amortized over its estimated useful life. The following is an expected amortization schedule for the intangible assets for the remainder of fiscal 2018 through fiscal 2022 , absent any future acquisitions or impairment charges (amounts in thousands): Fiscal Year Ending March 31, Projected Amortization Expense 2018 $122,252 2019 361,682 2020 313,484 2021 257,430 2022 190,429 Amortization expense attributed to intangible assets was $122.6 million and $368.1 million for the three and nine months ended December 31, 2017 , respectively. Amortization expense attributed to intangible assets was $85.2 million and $250.6 million for the three and nine months ended December 31, 2016 , respectively. In the three and nine months ended December 31, 2017 , approximately $1.5 million and $4.9 million of amortization expense, respectively, was charged to cost of sales, and approximately $121.1 million and $363.2 million , respectively, was charged to operating expenses. In the three and nine months ended December 31, 2016 , approximately $0.9 million and $2.8 million of amortization expense, respectively, was charged to cost of sales, and approximately $84.3 million and $247.8 million , respectively, was charged to operating expenses. The Company recognized an immaterial amount of intangible asset impairment charges in the three and nine months ended December 31, 2017 . In connection with its acquisition of Atmel, the Company recognized intangible asset impairment charges of $8.2 million and $10.2 million for the three and nine months ended December 31, 2016 , respectively. The impairment losses were recognized as a result of changes in the combined product roadmaps after the acquisition of Atmel that affected the use and life of these assets. The following shows the goodwill balance as of December 31, 2017 and March 31, 2017 by segment (amounts in thousands): Semiconductor Products Reporting Unit Technology Licensing Reporting Unit Goodwill $ 2,279,809 $ 19,200 At March 31, 2017 , the Company applied a qualitative goodwill impairment test to its two reporting units, concluding it was not more likely than not that goodwill was impaired. Through December 31, 2017 , the Company has never recorded an impairment charge against its goodwill balance.

Income Taxes (Notes)

Income Taxes (Notes)	9 Months Ended
	Dec. 31, 2017
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 227.7% for the three months ended December 31, 2017 and a negative effective tax rate of 28.5% for the three months ended December 31, 2016. The Company had an effective tax rate of 80.2% for the nine months ended December 31, 2017 and a negative effective tax rate of 87.3% for the nine months ended December 31, 2016 . On December 22, 2017, the Tax Cuts and Jobs Act (the "Act") was enacted into law. The Act provides for numerous significant tax law changes and modifications including the reduction of the U.S. federal corporate income tax rate from 35.0% to 21.0% , the requirement for companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and the creation of new taxes on certain foreign-sourced earnings. As a fiscal year-end taxpayer, certain provisions of the Act began to impact the Company in the third quarter of fiscal 2018, while other provisions will impact the Company beginning in fiscal 2019. The corporate tax rate reduction is effective as of January 1, 2018. Since the Company has a fiscal year rather than a calendar year, it is subject to rules relating to transitional tax rates. As a result, the Company’s fiscal 2018 federal statutory rate will be a blended rate of 31.5% . The change in the statutory tax rate from 35.0% to 31.5% for the Company's fiscal 2018 does not have a significant impact on the Company's effective tax rate. Accounting Standards Codification ("ASC") 740, Income Taxes, requires companies to recognize the effect of the tax law changes in the period of enactment. However, the SEC staff issued Staff Accounting Bulletin ("SAB") 118 which allows companies to record provisional amounts during a measurement period that is similar to the measurement period used when accounting for business combinations. The Company has recorded a reasonable estimate when possible and with the understanding that the provisional amount is subject to further adjustments under SAB 118. In addition, for significant items for which the Company could not make a reasonable estimate, no provisional amounts were recorded. Amounts will be recorded during the measurement period allowed under SAB 118 when a reasonable estimate can be made, or when the effect of the Act is known. As of December 31, 2017, the Company made a reasonable estimate of the effects on its existing deferred tax balances and the one-time transition tax. The Company recognized a provisional amount of $443.2 million , which decreased diluted net income per common share by $1.79 for the nine months ended December 31, 2017, and which was included as a component of income tax expense from continuing operations. The Company will continue to refine provisional balances and adjustments may be made under SAB 118 during the measurement period as a result of future changes in interpretation, information available, assumptions made by the Company and/or issuance of additional guidance and these adjustments could be material. The one-time transition tax is based on the Company's total post-1986 earnings and profits ("E&P") of its foreign subsidiaries. Substantially all of the Company's E&P were permanently reinvested outside the U.S prior to the Act. The Company recorded provisional U.S. amounts for its one-time transition tax liabilities, resulting in an increase in income tax expense of $627.7 million . In addition, the Company released the deferred tax liabilities related to non-permanently reinvested E&P, resulting in a decrease in income tax expense of $5.5 million . The net increase to tax expense is $622.2 million . The one-time transition tax may be elected to be paid over a period of eight years. The Company intends to make this election. The Company has not yet completed its calculation of the total post-1986 E&P for its foreign subsidiaries. In addition, the one-time transition tax is based in part on the amount of those earnings held in cash and other specified assets either as of the end of fiscal 2018 or the average of the year-end balances for fiscal 2016 and fiscal 2017. The Company's calculation of this amount will change with further analysis, fourth quarter activities, and further guidance from the U.S. federal and state tax authorities about the application of these new rules. The Company will continue to evaluate the impact of the tax law change as it relates to the accounting for the outside basis difference of its foreign entities. As a result of the reduction of the corporate income tax rate to 21.0% , U.S. GAAP requires companies to remeasure their deferred tax assets and liabilities as of the date of enactment, with resulting tax effects accounted for in the reporting period of enactment. The Company remeasured deferred tax assets and liabilities based on the rates at which they are expected to to be utilized in the future. The provisional amount recorded for the remeasurement and resulting income tax benefit of the Company's deferred tax balance was $142.6 million . The Company's actual income tax benefit may vary materially from the provisional amount because the final analysis will be based on balances as of March 31, 2018. Due to the Act, the Company released its valuation allowance on foreign tax credits during the three months ended December 31, 2017. The provisional amount recorded for the valuation allowance release was an income tax benefit of $36.4 million . The Company is still evaluating how the Act impacts the valuation allowance on state net operating loss carryforwards and state tax credits, and the Company may report an adjustment to the valuation allowances in accordance with SAB 118 in subsequent quarters. The Company's effective tax rate for the three and nine months ended December 31, 2017 is higher compared to the prior year primarily due to the one-time transition tax net of the reversal of the related deferred tax liabilities. The Company's effective tax rate is different than statutory rates in the U.S. due primarily to the one-time transition tax net of the reversal of the related deferred tax liabilities, as well as its mix of earnings in foreign jurisdictions with lower tax rates as well as numerous tax holidays it receives related to its Thailand manufacturing operations based on its investment in property, plant and equipment in Thailand. The Company's tax holiday periods in Thailand expire at various times in the future, however, the Company actively seeks to obtain new tax holidays. The Company does not expect the future expiration of any of its tax holiday periods in Thailand to have a material impact on its effected tax rate. The material components of foreign income taxed at a rate lower than the U.S. are earnings accrued in Thailand and Ireland, and earnings accrued by the Company's offshore technology company which is resident in the Cayman Islands. 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 2005 and later tax years remain effectively open for examination by tax authorities. For foreign tax returns, the Company is generally no longer subject to income tax examinations for years prior to fiscal 2007. The Company recognizes liabilities for anticipated tax audit issues in the U.S. and other domestic and international 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 and to be 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 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 or closure of audits is highly uncertain, the Company does not believe it is reasonably possible that the unrecognized tax benefits would materially change in the next 12 months.

Debt and Credit Facility (Notes

Debt and Credit Facility (Notes)	9 Months Ended
	Dec. 31, 2017
Convertible Debt [Abstract]
Debt and Credit Facility	Debt and Credit Facility Debt obligations included in the condensed consolidated balance sheets consisted of the following (in millions): Coupon Interest Rate Effective Interest Rate Fair Value of Liability Component at Issuance (1) December 31, 2017 March 31, 2017 Senior Indebtedness Credit Facility $ — $ — Senior Subordinated Convertible Debt - Principal Outstanding 2017 Senior Debt, maturing February 15, 2027 (2017 Senior Debt) 1.625% 6.0% $1,396.3 $ 2,070.0 $ 2,070.0 2015 Senior Debt, maturing February 15, 2025 (2015 Senior Debt) 1.625% 5.9% 1,160.1 1,725.0 1,725.0 Junior Subordinated Convertible Debt - Principal Outstanding 2017 Junior Debt, maturing February 15, 2037 (2017 Junior Debt) 2.250% 7.4% 321.1 686.3 575.0 2007 Junior Debt, maturing December 15, 2037 (2007 Junior Debt) 2.125% 9.1% — — 143.8 Total Convertible Debt 4,481.3 4,513.8 Gross long-term debt including current maturities 4,481.3 4,513.8 Less: Debt discount (2) (1,399.8 ) (1,516.5 ) Less: Debt issuance costs (3) (41.9 ) (46.8 ) Net long-term debt including current maturities 3,039.6 2,950.5 Less: Current maturities (4) — (50.0 ) Net long-term debt $ 3,039.6 $ 2,900.5 (1) As each of the convertible instruments may be settled in cash upon conversion, for accounting purposes, they were bifurcated into a liability component and an equity component, which are both initially recorded at fair value. The amount allocated to the equity component is the difference between the principal value of the instrument and the fair value of the liability component at issuance. The resulting debt discount is being amortized to interest expense at the respective effective interest rate over the contractual term of the debt. (2) The unamortized discount includes the following (in millions): December 31, March 31, 2017 2017 2017 Senior Debt $ (629.3 ) $ (667.5 ) 2015 Senior Debt (412.1 ) (446.6 ) 2017 Junior Debt (358.4 ) (309.3 ) 2007 Junior Debt — (93.1 ) Total unamortized discount $ (1,399.8 ) $ (1,516.5 ) (3) Debt issuance costs include the following (in millions): December 31, March 31, 2017 2017 Senior Credit Facility $ (6.7 ) $ (8.5 ) 2017 Senior Debt (16.5 ) (17.6 ) 2015 Senior Debt (15.3 ) (16.6 ) 2017 Junior Debt (3.4 ) (3.4 ) 2007 Junior Debt — (0.7 ) Total debt issuance costs $ (41.9 ) $ (46.8 ) (4) Current maturities include the full balance of the 2007 Junior Debt as of March 31, 2017. Ranking of Indebtedness - The Senior Subordinated Convertible Debt and Junior Subordinated Convertible Debt (collectively, the Convertible Debt) are unsecured obligations which are subordinated in right of payment to the amounts outstanding under the Company's Credit Facility. The Junior Subordinated Convertible Debt is expressly subordinated in right of payment to any existing and future senior debt of the Company (including the Credit Facility and the Senior Subordinated Convertible Debt) and is structurally subordinated in right of payment to the liabilities of the Company's subsidiaries. The Senior Subordinated Convertible Debt is subordinated to the Credit Facility; ranks senior to the Company's indebtedness that is expressly subordinated in right of payment, including the Junior Subordinated Convertible Debt; ranks equal in right of payment to any of the Company's unsubordinated indebtedness that does not provide that it is senior to the Senior Subordinated Convertible Debt; ranks junior in right of payment to any of the Company's secured, unsubordinated indebtedness to the extent of the value of the assets securing such indebtedness; and ranks junior to all indebtedness and other liabilities of the Company's subsidiaries. Summary of Conversion Features - Each series of Convertible Debt is convertible, subject to certain conditions, into cash, shares of the Company's common stock or a combination thereof, at the Company's election, at specified Conversion Rates (see table below), adjusted for certain events including the declaration of cash dividends. Until the three-months immediately preceding the maturity date of the applicable series of Convertible Debt, each series of Convertible Debt is convertible only upon the occurrence of (1) such time as the closing price of the Company's common stock exceeds the Conversion Price (see table below) by 130% for 20 days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding fiscal quarter or (2) during the 5 business day period after any 10 consecutive trading day period, or the measurement period, in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company's common stock and the conversion rate on each such trading day or (3) upon the occurrence of certain corporate events specified in the indenture of such series of Convertible Debt. In addition, for each series, if at the time of conversion the applicable price of the Company's common stock exceeds the applicable Conversion Price at such time, the applicable Conversion Rate will be increased by up to an additional maximum incremental shares rate, as determined pursuant to a formula specified in the indenture for the applicable series of Convertible Debt, and as adjusted for cash dividends paid since the issuance of such series of Convertible Debt. However, in no event will the applicable Conversion Rate exceed the applicable Maximum Conversion Rate specified in the indenture for the applicable series of Convertible Debt (see table below). The following table sets forth the applicable Conversion Rates adjusted for dividends declared since issuance of such series of Convertible Debt and the applicable Incremental Share Factors and Maximum Conversion Rates as adjusted for dividends paid since the applicable issuance date: Dividend adjusted rates as of December 31, 2017 Conversion Rate, adjusted Approximate Conversion Price, adjusted Incremental Share Factor, adjusted Maximum Conversion Rate, adjusted 2017 Senior Debt 10.0722 $ 99.28 5.0361 14.3529 2015 Senior Debt 15.7069 $ 63.67 7.8534 21.9896 2017 Junior Debt 10.2521 $ 97.54 5.1261 14.3529 As of December 31, 2017 , the holders of the 2015 Senior Debt have the right to convert their debentures between January 1, 2018 and March 31, 2018 because the Company's common stock price has exceeded the Conversion Price by 130% for the specified period of time during the quarter ended December 31, 2017 . As of December 31, 2017 , the 2015 Senior Debt is convertible and had a value if converted above par of $1,108.8 million . The Company may not redeem any series of Convertible Debt prior to the relevant maturity date and no sinking fund is provided for any series of Convertible Debt. Upon the occurrence of a fundamental change as defined in the applicable indenture of such series of Convertible Debt, holders of such series may require the Company to purchase all or a portion of their Convertible Debt for cash at a price equal to 100% of the principal amount plus any accrued and unpaid interest. Interest expense related to convertible debt includes the following (in millions): Three Months Ended Nine Months Ended December 31, 2017 2016 2017 2016 Debt issuance amortization $ 0.9 $ 0.5 $ 2.7 $ 1.3 Amortization of debt discount - non cash interest expense 26.7 12.5 79.0 36.9 Coupon interest expense 19.3 10.1 58.1 30.3 Total $ 46.9 $ 23.1 $ 139.8 $ 68.5 The remaining period over which the unamortized debt discount will be recognized as non-cash interest expense is 9.13 years , 7.13 years , and 19.13 years for the 2017 Senior Debt, 2015 Senior Debt, and 2017 Junior Debt, respectively. Issuances and Settlements - In November 2017, the Company called $14.6 million in principal value of the remaining outstanding 2007 Junior Debt with an effective date of December 15, 2017 for which substantially all holders submitted requests to convert. Prior to the call, conversion requests were received in both the second and third quarters of fiscal 2018. Total conversions for the six months ending December 31, 2017 were for a principal amount of $32.4 million for which the Company settled the principal amount in cash and issued 0.5 million shares of its common stock in respect of the conversion value in excess of the principal amount for the conversions occurring prior to the call notice and $41.0 million in cash for the conversion value in excess of the principal amount for the conversion requests received after the call notice. A loss on total conversions for the six months ended December 31, 2017 was recorded for $2.1 million . The 2007 Junior Debt was classified as a current liability on the consolidated balance sheet as of March 31, 2017. In June 2017, the Company exchanged in privately negotiated transactions $111.3 million aggregate principal amount of its 2007 Junior Debt for (i) $111.3 million principal amount of 2017 Junior Debt with a market value of $119.3 million plus (ii) the issuance of 3.2 million shares of the Company's common stock with a value of $254.6 million , of which $56.3 million was allocated to the fair value of the liability and $321.1 million was allocated to the reacquisition of the equity component for total consideration of $374.0 million . The transaction resulted in a loss on settlement of the 2007 Junior Debt of approximately $13.8 million , which represented the difference between the fair value of the liability component at time of repurchase and the sum of the carrying values of the debt component and any unamortized debt issuance costs. The debt discount on the new 2017 Junior Debt was the difference between the par value and the fair value of the debt resulting in a debt discount of $55.1 million which will be amortized to interest expense using the effective interest method over the term of the debt. In February 2017, the Company issued the 2017 Senior Debt and 2017 Junior Debt for net proceeds of $2,043.6 million and $567.7 million , respectively. In connection with the issuance of these instruments, the Company incurred issuance costs of $33.7 million , of which $17.8 million and $3.4 million was recorded as debt issuance costs related to the 2017 Senior Debt and 2017 Junior Debt, respectively, and will be amortized using the effective interest method over the term of the debt. The balance of $12.5 million in fees was recorded to equity. Interest on both instruments is payable semi-annually on February 15 and August 15 of each year. In February 2015, the Company issued the 2015 Senior Debt for net proceeds of approximately $1,694.7 million . In connection with the issuance, the Company incurred issuance costs of $30.3 million , of which $20.4 million was recorded as debt issuance costs and will be amortized using the effective interest method over the term of the debt. The balance of $9.9 million was recorded to equity. The Company utilized the proceeds from the issuances of the 2017 Senior Debt, 2017 Junior Debt, and 2015 Senior Debt to reduce amounts borrowed under its Credit Facility and to settle a portion of the 2007 Junior Debt in privately negotiated transactions. In February 2017 and February 2015, the Company settled $431.3 million and $575.0 million , respectively, in aggregate principal of its 2007 Junior Debt. The 2015 repurchase consisted solely of cash. In February 2017, the Company used cash of $431.3 million and an aggregate of 12.0 million in shares of the Company's common stock valued at $862.7 million for total consideration of $1,293.9 million to settle $431.3 million of the 2007 Junior Debt, of which $188.0 million was allocated to the liability component and $1,105.9 million was allocated to the equity component. In addition, in February 2017, there was an inducement fee of $5.0 million which was recorded in the consolidated statements of operations in loss on settlement of convertible debt. The consideration transferred in February 2015 was $1,134.6 million , of which $238.3 million was allocated to the liability component and $896.3 million was allocated to the equity component. In the case of both settlements of the 2007 Junior Debt, the consideration was allocated to the liability and equity components using the equivalent rate that reflected the borrowing rate for a similar non-convertible debt prior to the retirement. The transactions resulted in a loss on settlement of convertible debt of approximately $43.9 million and $50.6 million in fiscal 2017 and fiscal 2015, respectively, which represented, in each case, the difference between the fair value of the liability component at time of repurchase and the sum of the carrying values of the debt component and any unamortized debt issuance costs. Credit Facility The Company maintains a credit facility which is available until February 4, 2020 (the "Credit Agreement"). At the beginning of the second quarter of fiscal 2018, the credit facility had a borrowing capacity of $2.774 billion comprised of two tranches; one tranche terminating in 2018 (the "2018 Tranche") and one tranche terminating in 2020 (the "2020 Tranche"). During the second quarter of fiscal 2018, the Company terminated the 2018 Tranche and in connection with such termination increased the commitments for the 2020 Tranche in each of the three months ended September 30, 2017 and December 31, 2017. In November 2017, the Company entered into an augmenting lender supplement which added a new lender to the Credit Agreement with a 2020 multicurrency tranche commitment. As of December 31, 2017, the 2020 Tranche commitment under the credit facility was $3.122 billion . The financial covenants include, among others, limits on the Company's consolidated senior ratio and total leverage ratio. The maximum Total Leverage Ratio (capitalized terms not otherwise defined in this Form 10-Q have the meaning of the defined terms in the applicable agreements) cannot exceed 5.00 to 1.00 and is calculated as Consolidated Total Indebtedness, excluding the Junior Debt up to a $700 million maximum, to Consolidated EBIDTA for a period of four quarters. The Total Leverage Ratio may be temporarily increased to 5.50 to 1.00 for a period of four consecutive quarters in conjunction with a Permitted Acquisition occurring during the first four quarters following the acquisition. The Total Leverage Ratio then decreases to 5.25 to 1.00 for three consecutive quarters, finally returning to the stated 5.00 to 1.00 Total Leverage Ratio after a period of seven consecutive fiscal periods. The Company can elect to use this special feature, also referred to as an Adjusted Covenant Period, not more than one time from and after February 8, 2017, the effective date of the February 2017 amendment (discussed below), and may elect to terminate an Adjusted Covenant Period prior to the end of the Adjusted Covenant Period. The Credit Facility also requires that the Senior Leverage Ratio not exceed 3.50 to 1.00, which is calculated as Consolidated Senior Indebtedness to Consolidated EBIDTA for four consecutive quarters. The Company is also required to comply with an Interest Coverage Ratio of less than 3.50 to 1.00, measured quarterly. In June 2017, in connection with the settlement of the 2007 Junior Debt, the Company amended the Credit Agreement to (i) extend the time period during which the Company is permitted to repurchase, redeem or exchange the 2007 Junior Debt and (ii) amend the maximum total leverage ratio covenant to extend the time period for permitted refinancings or exchanges of the 2007 Junior Debt that may be excluded from the calculation of the ratio, subject to certain conditions. The Credit Agreement has a $ 125 million foreign currency sublimit, a $ 25 million letter of credit sublimit and a $25 million swingline loan sublimit. The Company has the option to obtain additional tranche commitments or additional indebtedness as long as the Senior Leverage Ratio is equal to or less than 2.50 to 1.00. In February 2017, the Company used $1,682.5 million of the proceeds from the issuance of the 2017 Senior Debt and 2017 Junior Debt to pay off the entire balance on its line of credit. In connection with the February 2017 amendment to the Credit Agreement, the Company incurred $2.1 million of issuance fees which will be amortized over the term of the facility and for which the balance is recorded net of any outstanding Credit Facility balance. At December 31, 2017 and March 31, 2017 , there were no outstanding borrowings under the revolving credit facility. 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 are required to pledge the equity securities of certain of their respective material subsidiaries, subject to certain exceptions and limitations. In addition, in connection with the February 2017 amendment, the Company and the guarantor subsidiaries granted a security interest in substantially all of their personal property to secure the obligations under the Credit Agreement. 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 quarters (in the case of the 2018 tranche revolving loans) or the consolidated senior leverage ratio (in the case of the 2020 tranche revolving loans). 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 $2.3 million and $7.3 million in the three and nine months ended December 31, 2017 , respectively, compared to $11.9 million and $35.5 million for the three and nine months ended December 31, 2016 , respectively. Principal, together with all accrued and unpaid interest, is due and payable on the tranche maturity date, which is February 4, 2020. The Company pays a quarterly commitment fee on the available but unused portion of its line of credit which is calculated on the average daily available balance during the period. 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 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 senior leverage ratio, a total leverage ratio and an interest coverage ratio, all measured quarterly and calculated on a consolidated bases. At December 31, 2017 , 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.

Pension Plans (Notes)

Pension Plans (Notes)	9 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Pension Plans	Pension Plans In connection with its acquisition of Atmel, the Company assumed unfunded defined benefit pension plans that cover certain French and German employees. Plan benefits are provided in accordance with local statutory requirements. Benefits are based on years of service and employee compensation levels. Pension liabilities and charges are based upon various assumptions, updated annually, including discount rates, future salary increases, employee turnover, and mortality rates. The Company's French pension plan provides for termination benefits paid to covered French employees only at retirement, and consists of approximately one to five months of salary. The Company's German pension plan provides for defined benefit payouts for covered German employees following retirement. The aggregate net pension expense relating to these two plans are as follows (amounts in thousands): Three Months Ended Nine Months Ended December 31, December 31, 2017 2016 2017 2016 Service costs $ 390 $ 327 $ 1,131 $ 1,054 Interest costs 253 214 742 698 Amortization of actuarial loss 214 — 630 — Settlements and curtailments — 354 (36 ) 585 Net pension period cost $ 857 $ 895 $ 2,467 $ 2,337 Interest costs and amortization of actuarial losses are recorded in the other income, net line item in the statements of operations. The Company's net periodic pension cost for fiscal 2018 is expected to be approximately $ 3.3 million . Cash funding for benefits paid was $0.3 million and $0.6 million for the three and nine months ended December 31, 2017 , respectively, and $0.1 million and $0.3 million for the three and nine months ended December 31, 2016 , respectively. The Company expects total contributions to these plans to be approximately $ 0.7 million in fiscal 2018.

Contingencies (Notes)

Contingencies (Notes)	9 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies In the ordinary course of the Company's business, it is exposed to various liabilities as a result of contracts, product liability, customer claims and other matters. Additionally, the Company is involved in a limited number of legal actions, both as plaintiff and defendant. Consequently, the Company could incur uninsured liability in any of those actions. The Company also periodically receives notifications from various third parties alleging infringement of patents or other intellectual property rights, or from customers requesting reimbursement for various costs. With respect to pending legal actions to which the Company is a party and other claims, although the outcomes are generally not 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 and disputes relating to the semiconductor industry are not uncommon, and the Company is, from time to time, subject to such litigation and disputes. As a result, no assurances can be given with respect to the extent or outcome of any such litigation or disputes in the future. As a result of its acquisition of Atmel, which closed April 4, 2016, the Company became involved with the following legal matters: In re: Continental Airbag Products Liability Litigation . On May 11, 2016, an Amended and Consolidated Class Action Complaint ("Complaint") was filed in the United States District Court for the Southern District of Florida (Miami Division) against Atmel, Continental Automotive Systems, Inc., Honda Motor Co., Ltd. and an affiliate, and Daimler AG and an affiliate. The Complaint included claims arising under federal law and Florida, California, New Jersey, Michigan and Louisiana state law and alleged that class members unknowingly purchased or leased vehicles containing defective airbag control units (incorporating allegedly defective application specific integrated circuits manufactured by the Company's Atmel subsidiary between 2006 and 2010), and thereby suffered financial harm, including a loss in the value of their purchased or leased vehicles. The plaintiffs were seeking, individually and on behalf of a putative class, unspecified compensatory and exemplary damages, statutory penalties, pre- and post-judgment interest, attorneys' fees, and injunctive and other relief. The Company's Atmel subsidiary contested plaintiffs' claims vigorously, and on May 23, 2017 the case was ordered to be dismissed. Continental Claim ICC Arbitration. On December 29, 2016, Continental Automotive GmbH ("Continental") filed a Request for Arbitration with the ICC, naming as respondents the Company's subsidiaries Atmel Corporation, Atmel SARL, Atmel Global Sales Ltd., and Atmel Automotive GmbH (collectively, "Atmel"). The Request alleges that a quality issue affecting Continental airbag control units in certain recalled vehicles stems from allegedly defective Atmel application specific integrated circuits ("ASICs"). The Continental airbag control units, ASICs and vehicle recalls were also at issue in In re: Continental Airbag Products Liability Litigation , described above. Continental seeks to recover from Atmel all related costs and damages incurred as a result of the vehicle manufacturers’ airbag control unit-related recalls, currently alleged to be $69.7 million (but subject to increase). The Company's Atmel subsidiaries intend to defend this action vigorously. Southern District of New York Action by LFoundry Rousset ("LFR") and LFR Employees . On March 4, 2014, LFR and Jean-Yves Guerrini, individually and on behalf of a putative class of LFR employees, filed an action in the United States District Court for the Southern District of New York (the "District Court") against the Company's Atmel subsidiary, French subsidiary, Atmel Rousset S.A.S. ("Atmel Rousset"), and LFoundry GmbH ("LF"), LFR's German parent. The case purports to relate to Atmel Rousset's June 2010 sale of its wafer manufacturing facility in Rousset, France to LF, and LFR's subsequent insolvency, and later liquidation, more than three years later. The District Court dismissed the case on August 21, 2015, and the United States Court of Appeals for the Second Circuit affirmed the dismissal on June 27, 2016. On July 25, 2016, the plaintiffs filed a notice of appeal from the District Court's June 27, 2016 denial of their motion for relief from the dismissal judgment. On May 19, 2017, the United States Court of Appeals for the Second Circuit affirmed the June 27, 2016 order dismissing the case. Individual Labor Actions by former LFR Employees . In the wake of LFR's insolvency and liquidation, over 500 former employees of LFR have filed individual labor actions against Atmel Rousset in a French labor court. The Company's Atmel Rousset subsidiary believes that each of these actions is entirely devoid of merit, and, further, that any assertion by any of the Claimants of a co-employment relationship with the Atmel Rousset subsidiary is based substantially on the same specious arguments that the Paris Commercial Court summarily rejected in 2014 in related proceedings. The Company's Atmel Rousset subsidiary therefore intends to defend vigorously against each of these claims. Additionally, complaints have been filed in a regional court in France on behalf of the same group of employees against Microchip Technology Rousset, Atmel Switzerland Sarl, Atmel Corporation and Microchip Technology Incorporated alleging that the sale of the Atmel Rousset production unit to LFoundry GmbH was fraudulent and should be voided. These claims are based largely on the same specious arguments as listed in the Southern District of New York Action listed above. The defendant entities therefore intend to defend vigorously against these claims. The Company accrues for claims and contingencies when losses become probable and reasonably estimable. As of the end of each applicable reporting period, the Company reviews each of its matters and, where it is probable that a liability has been or will be incurred, the Company accrues for all probable and reasonably estimable losses. Where the Company can reasonably estimate a range of losses it may incur regarding such a matter, the Company records an accrual for the amount within the range that constitutes its best estimate. If the Company can reasonably estimate a range but no amount within the range appears to be a better estimate than any other, the Company uses the amount that is the low end of such range. As of December 31, 2017 , the Company's estimate of the aggregate potential liability that is possible but not probable is approximately $100 million in excess of amounts accrued. 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 $159.0 million . There are some licensing agreements in place that do not specify indemnification limits. As of December 31, 2017 , the Company had not recorded any liabilities related to these indemnification obligations and the Company believes that any amounts that it may be required to pay under these agreements in the future will not have a material adverse effect on its financial position, cash flows or results of operations.

Derivative Instruments (Notes)

Derivative Instruments (Notes)	9 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments Freestanding Derivative Forward Contracts The Company has international operations and is thus subject to foreign currency rate fluctuations. Approximately 99% of the Company's sales are U.S. Dollar denominated. However, a significant amount of the Company's expenses and liabilities are denominated in foreign currencies and 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. Foreign exchange rate fluctuations after the effects of hedging activity resulted in net losses of $2.4 million for the three months ended December 31, 2017 and net gains of $7.1 million during the nine months ended December 31, 2017 , compared to net gains of $1.3 million for the three months ended December 31, 2016 and net losses of $0.8 million during the nine months ended December 31, 2016 . As of December 31, 2017 and March 31, 2017 , the Company had no foreign currency forward contracts outstanding. The Company recognized net realized gains on foreign currency forward contracts of $0.3 million and $3.5 million in the three and nine months ended December 31, 2017 , respectively. The Company recognized net realized losses on foreign currency forward contracts of $3.1 million in each of the three and nine months ended December 31, 2016. Gains and losses from changes in the fair value of these foreign currency forward contracts and foreign currency exchange rate fluctuations are credited or charged to other income (expense). The Company does not apply hedge accounting to its foreign currency derivative instruments. Commodity Price Risk The Company is exposed to fluctuations in prices for energy that it consumes, particularly electricity and natural gas. The Company also enters into variable-priced contracts for some purchases of electricity and natural gas, on an index basis. The Company seeks, or may seek, to partially mitigate these exposures through fixed-price contracts. These contracts meet the characteristics of derivative instruments, but generally qualify for the “normal purchases or normal sales” exception under authoritative guidance and require no mark-to-market adjustment.

Comprehensive (Loss) Income (No

Comprehensive (Loss) Income (Notes)	9 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Comprehensive (Loss) Income	Comprehensive (Loss) Income The following table presents the changes in the components of accumulated other comprehensive (loss) income (AOCI), net of tax, for the nine months ended December 31, 2017 (amounts in thousands): Unrealized holding gains (losses) available-for-sale securities Defined benefit pension plans Foreign Currency Total Accumulated other comprehensive income (loss) at March 31, 2017 $ 312 $ (5,263 ) $ (9,427 ) $ (14,378 ) Other comprehensive loss before reclassifications (6,161 ) (2,284 ) — (8,445 ) Amounts reclassified from accumulated other comprehensive loss — 630 — 630 Net other comprehensive loss (6,161 ) (1,654 ) — (7,815 ) Accumulated other comprehensive loss at December 31, 2017 $ (5,849 ) $ (6,917 ) $ (9,427 ) $ (22,193 ) The table below details where reclassifications of realized transactions out of AOCI are recorded on the condensed consolidated statements of operations (amounts in thousands): Three Months Ended Nine Months Ended December 31, December 31, Description of AOCI Component 2017 2016 2017 2016 Related Statement of Income Line Unrealized losses on available-for-sale securities $ — $ (1,433 ) $ — $ (1,522 ) Other income (loss) Amortization of actuarial loss (214 ) — (630 ) — Other income (loss) Reclassification of realized transactions, net of taxes $ (214 ) $ (1,433 ) $ (630 ) $ (1,522 ) Net income

Share-Based Compensation (Notes

Share-Based Compensation (Notes)	9 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	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, 2017 2016 2017 2016 Cost of sales (1) $ 3,494 $ 3,468 $ 10,587 $ 15,465 Research and development 10,921 9,881 31,797 37,569 Selling, general and administrative 9,588 8,771 27,637 53,055 Pre-tax effect of share-based compensation 24,003 22,120 70,021 106,089 Income tax benefit (2) 6,604 7,376 21,878 36,622 Net income effect of share-based compensation $ 17,399 $ 14,744 $ 48,143 $ 69,467 (1) During the three and nine months ended December 31, 2017 , $3.1 million and $8.9 million , respectively, of share-based compensation expense was capitalized to inventory and $3.5 million and $10.6 million , respectively, of previously capitalized share-based compensation expense in inventory was sold. During the three and nine months ended December 31, 2016 , $2.8 million and $8.3 million , respectively, of share-based compensation expense was capitalized to inventory. The amount of share-based compensation included in cost of sales during the three months ended December 31, 2016 included $3.5 million of previously capitalized share-based compensation expense in inventory that was sold. The amount of share-based compensation included in cost of sales during the nine months ended December 31, 2016 included $11.3 million of previously capitalized share-based compensation expense in inventory that was sold and $4.2 million of share-based compensation expense related to the Company's acquisition of Atmel that was not previously capitalized to inventory. (2) Amounts exclude excess tax benefits related to share-based compensation of $5.7 million and $19.8 million , respectively, for the three and nine months ended December 31, 2017 and $6.1 million and $18.6 million , respectively, for the three and nine months ended December 31, 2016 . Atmel Acquisition-related Equity Awards During the three months ended December 31, 2016 , the Company recognized $3.9 million of share-based compensation expense in connection with the acquisition of Atmel. During the nine months ended December 31, 2016 , the Company recognized $ 53.3 million of share-based compensation expense in connection with awards assumed in the acquisition of Atmel, of which $ 38.8 million was due to the accelerated vesting of outstanding equity awards upon termination of certain Atmel employees.

Net (Loss) Income Per Common Sh

Net (Loss) Income Per Common Share From Continuing Operations (Notes)	9 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net (Loss) Income Per Common Share From Continuing Operations	Net (Loss) Income Per Common Share From Continuing Operations The following table sets forth the computation of basic and diluted net (loss) income per common share from continuing operations (in thousands, except per share amounts): Three Months Ended Nine Months Ended December 31, December 31, 2017 2016 2017 2016 Net (loss) income from continuing operations $ (251,086 ) $ 107,335 $ 108,657 $ 33,684 Weighted average common shares outstanding 234,106 216,210 232,278 215,360 Dilutive effect of stock options and RSUs — 4,330 4,460 4,317 Dilutive effect of 2007 Junior debt — 14,884 1,735 13,674 Dilutive effect of 2015 Senior debt — — 9,551 — Dilutive effect of 2017 Senior debt — — — — Dilutive effect of 2017 Junior debt — — — — Weighted average common and potential common shares outstanding 234,106 235,424 248,024 233,351 Basic net (loss) income per common share from continuing operations $ (1.07 ) $ 0.50 $ 0.47 $ 0.16 Diluted net (loss) income per common share from continuing operations $ (1.07 ) $ 0.46 $ 0.44 $ 0.14 The Company computed basic net (loss) income per common share from continuing operations using net (loss) income from continuing operations and the weighted average number of common shares outstanding during the period. The Company computed diluted net (loss) income per common share from continuing operations using net (loss) income from continuing operations and the weighted average number of common shares outstanding plus potentially dilutive common shares outstanding during the period. Potentially dilutive common shares from employee equity incentive plans are determined by applying the treasury stock method to the assumed exercise of outstanding stock options and the assumed vesting of outstanding RSUs. Weighted average common shares exclude the effect of option shares which are not dilutive. For the three months ended December 31, 2017, the calculation of diluted net loss per common share excluded 4,400,046 common shares from employee equity incentive plans as the related impact would have been anti-dilutive as the Company generated a net loss. There were no anti-dilutive option shares for the nine months ended December 31, 2017 , and the three and nine months ended December 31, 2016 . For the three months ended December 31, 2017, the calculation of diluted net loss per common share excluded 398,430 shares and 11,920,246 shares issuable upon the exchange of the Company's 2007 Junior Debt, and the Company's 2015 Senior Debt, respectively, as the related impact would have been anti-dilutive as the Company generated a net loss. Diluted net income per common share from continuing operations for the nine months ended December 31, 2017 , includes 1,734,984 shares and 9,551,342 shares issuable upon the exchange of the Company's 2007 Junior Debt, and the Company's 2015 Senior Debt, respectively. The Company's 2007 Junior Debt was fully settled as of December 31, 2017. Diluted net income per common share from continuing operations for the three and nine months ended December 31, 2016 included 14,883,643 shares and 13,673,578 shares issuable upon the exchange of the Company's 2007 Junior Debt, respectively (see Note 13 for details on the convertible debt). The convertible debt has 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 following is the weighted average conversion price per share used in calculating the dilutive effect (See Note 13 for details on the convertible debt): Three Months Ended Nine Months Ended December 31, December 31, 2017 2016 2017 2016 2007 Junior Debt $ 23.49 $ 23.93 $ 23.59 $ 24.08 2015 Senior Debt $ 63.80 $ 65.00 $ 64.07 $ 65.40 2017 Senior Debt $ 99.50 $ — $ 99.92 $ — 2017 Junior Debt $ 97.75 $ — $ 98.16 $ —

Stock Repurchase (Notes)

Stock Repurchase (Notes)	9 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stock Repurchase	Stock Repurchase The Company's Board of Directors previously approved a share repurchase program under which up to 15.0 million shares of common stock may be repurchased in the open market or in privately negotiated transactions. There were no repurchases of common stock during the three and nine months ended December 31, 2017 . There is no expiration date associated with this repurchase program. As of December 31, 2017 , the Company held approximately 18.9 million shares as treasury shares.

Dividends (Notes)

Dividends (Notes)	9 Months Ended
	Dec. 31, 2017
Dividends [Abstract]
Dividends	Dividends A quarterly cash dividend of $0.3625 per share was paid on December 5, 2017 in the aggregate amount of $84.9 million . Through the first nine months of fiscal 2018 , cash dividends of $1.0860 per share have been paid in the aggregate amount of $252.4 million . A quarterly cash dividend of $0.3630 per share was declared on February 6, 2018 and will be paid on March 6, 2018 to stockholders of record as of February 21, 2018 . The Company expects the March 6, 2018 payment of its quarterly cash dividend to be approximately $85.2 million .

Business Acquisitions (Tables)

Business Acquisitions (Tables) - Atmel Corporation	9 Months Ended
	Dec. 31, 2017
Business Acquisition [Line Items]
Schedule of recognized identified assets acquired and liabilities assumed	The table below represents the allocation of the final purchase price to the net assets acquired based on their estimated fair values, as well as the associated estimated useful lives of the acquired intangible assets (amounts in thousands). Assets acquired Cash and cash equivalents $ 230,266 Accounts receivable 141,359 Inventories 335,163 Prepaid expenses and other current assets 28,360 Assets held for sale 32,006 Property, plant and equipment 129,884 Goodwill 1,286,371 Purchased intangible assets 1,888,392 Long-term deferred tax assets 46,700 Other assets 7,535 Total assets acquired 4,126,036 Liabilities assumed Accounts payable (55,686 ) Other current liabilities (120,955 ) Long-term line of credit (192,000 ) Deferred tax liabilities (27,552 ) Long-term income tax payable (115,177 ) Other long-term liabilities (141,688 ) Total liabilities assumed (653,058 ) Purchase price allocated $ 3,472,978
Finite-lived and indefinite-lived intangible assets acquired as part of business combination	Purchased Intangible Assets Weighted Average Useful Life (in years) (in thousands) Core and developed technology 11 $ 1,074,987 In-process research and development — 140,700 Customer-related 6 630,600 Backlog 1 40,300 Other 5 1,805 Total purchased intangible assets $ 1,888,392

Discontinued Operations (Tables

Discontinued Operations (Tables)	9 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Disposal groups, including discontinued operations	The results of discontinued operations for the three and nine months ended December 31, 2016 are as follows (amounts in thousands): December 31, 2016 Three Months Ended Nine Months Ended Net sales $ 923 $ 18,334 Cost of sales 478 15,841 Operating expenses 1,279 10,650 Gain on Sale 643 643 Income tax benefit (31 ) (1,561 ) Net loss from discontinued operations $ (160 ) $ (5,953 )

Special Charges and Other, Ne33

Special Charges and Other, Net (Tables)	9 Months Ended
	Dec. 31, 2017
Other Nonrecurring (Income) Expense [Abstract]
Restructuring and Related Costs	The following table summarizes activity included in the "special charges and other, net" caption on the Company's condensed consolidated statements of operations (amounts in thousands): Three Months Ended Nine Months Ended December 31, December 31, 2017 2016 2017 2016 Restructuring Employee separation costs $ 90 $ 6,525 $ 1,477 $ 35,346 Gain on sale of assets — — (4,447 ) — Impairment charges 99 8,084 199 10,045 Contract exit costs (97 ) 4,954 20,057 5,294 Other 104 1,381 26 1,837 Total $ 196 $ 20,944 $ 17,312 $ 52,522 The following is a roll forward of accrued restructuring charges from April 1, 2017 to December 31, 2017 (amounts in thousands): Employee Separation Costs Exit Costs Total Balance at April 1, 2017 - Restructuring Accrual $ 5,474 $ 34,751 $ 40,225 Charges 1,477 20,057 21,534 Payments (4,755 ) (7,090 ) (11,845 ) Non-cash - Other (287 ) 869 582 Foreign exchange gains 272 — 272 Balance at December 31, 2017 - Restructuring Accrual $ 2,181 $ 48,587 $ 50,768 Current $ 14,042 Non-current 36,726 Total $ 50,768

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Net sales 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, 2017 (amounts in thousands): Three Months Ended Nine Months Ended December 31, 2017 December 31, 2017 Net Sales Gross Profit Net Sales Gross Profit Semiconductor products $ 966,678 $ 579,532 $ 2,900,145 $ 1,727,252 Technology licensing 27,527 27,527 78,340 78,340 Total $ 994,205 $ 607,059 $ 2,978,485 $ 1,805,592 The following table represents net sales and gross profit for each segment for the three and nine months ended December 31, 2016 (amounts in thousands): Three Months Ended Nine Months Ended December 31, 2016 December 31, 2016 Net Sales Gross Profit Net Sales Gross Profit Semiconductor products $ 810,532 $ 441,425 $ 2,437,049 $ 1,156,278 Technology licensing 23,834 23,834 68,092 68,092 Total $ 834,366 $ 465,259 $ 2,505,141 $ 1,224,370

Investments (Tables)

Investments (Tables)	9 Months Ended
	Dec. 31, 2017
Investments [Abstract]
Summary of available-for-sale securities	The following is a summary of available-for-sale securities at December 31, 2017 (amounts in thousands): Available-for-sale Securities Adjusted Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Government agency bonds $ 815,940 $ — $ (5,809 ) $ 810,131 Municipal bonds - taxable 10,000 — (57 ) 9,943 Corporate bonds and debt 491,851 — (1,484 ) 490,367 Marketable equity securities 707 1,758 — 2,465 Total $ 1,318,498 $ 1,758 $ (7,350 ) $ 1,312,906 The following is a summary of available-for-sale securities at March 31, 2017 (amounts in thousands): Available-for-sale Securities Adjusted Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Government agency bonds $ 227,089 $ 3 $ (227 ) $ 226,865 Municipal bonds - tax-exempt 55,289 — (10 ) 55,279 Municipal bonds - taxable 10,000 43 — 10,043 Corporate bonds and debt 207,888 53 (169 ) 207,772 Marketable equity securities 707 879 — 1,586 Total $ 500,973 $ 978 $ (406 ) $ 501,545
Summary of available-for-sale securities in a continuous unrealized loss position	The following tables show all investments in an unrealized loss position for which an other-than-temporary impairment has not been recognized and the related gross unrealized losses and fair value, aggregated by investment category and the length of time that the individual securities have been in a continuous unrealized loss position (amounts in thousands): December 31, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Government agency bonds $ 790,325 $ (5,615 ) $ 19,806 $ (194 ) $ 810,131 $ (5,809 ) Municipal bonds - taxable 9,943 (57 ) — — 9,943 (57 ) Corporate bonds and debt 447,061 (1,484 ) — — 447,061 (1,484 ) Total $ 1,247,329 $ (7,156 ) $ 19,806 $ (194 ) $ 1,267,135 $ (7,350 ) March 31, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Government agency bonds $ 196,875 $ (227 ) $ — $ — $ 196,875 $ (227 ) Municipal bonds - tax exempt 55,279 (10 ) — — 55,279 (10 ) Corporate bonds and debt 132,820 (169 ) — — 132,820 (169 ) Total $ 384,974 $ (406 ) $ — $ — $ 384,974 $ (406 )
Summary of investments classified by contractual maturity date	The amortized cost and estimated fair value of the available-for-sale securities at December 31, 2017 , by contractual maturity, excluding marketable equity securities of $2.5 million , which have 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 Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available-for-sale Due in one year or less $ 425,436 $ — $ (387 ) $ 425,049 Due after one year and through five years 892,355 — (6,963 ) 885,392 Due after five years and through ten years — — — — Total $ 1,317,791 $ — $ (7,350 ) $ 1,310,441

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Dec. 31, 2017
Fair Value, Assets, Liabilities and Stockholders' Equity 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, 2017 are as follows (amounts in thousands): Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Total Balance Assets Cash and cash equivalents: Money market mutual funds $ 108,204 $ — $ 108,204 Deposit accounts — 563,875 563,875 Short-term investments: Marketable equity securities 2,465 — 2,465 Corporate bonds and debt — 288,224 288,224 Government agency bonds — 136,825 136,825 Long-term investments: Corporate bonds and debt — 202,143 202,143 Government agency bonds — 673,306 673,306 Municipal bonds - taxable — 9,943 9,943 Total assets measured at fair value $ 110,669 $ 1,874,316 $ 1,984,985 Assets measured at fair value on a recurring basis at March 31, 2017 are as follows (amounts in thousands): Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Total Balance Assets Cash and cash equivalents: Money market mutual funds $ 343,815 $ — $ 343,815 Deposit accounts — 564,869 564,869 Short-term investments: Marketable equity securities 1,586 — 1,586 Corporate bonds and debt — 165,207 165,207 Government agency bonds — 161,973 161,973 Municipal bonds - tax-exempt — 55,279 55,279 Municipal bonds - taxable — 10,043 10,043 Long-term investments: Corporate bonds and debt — 42,565 42,565 Government agency bonds — 64,892 64,892 Total assets measured at fair value $ 345,401 $ 1,064,828 $ 1,410,229

Fair Value of Financial Instr37

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Carrying amounts and fair values of subordinated convertible debentures	The following table shows the carrying amounts and fair values of the Company's senior and junior subordinated convertible debt as of December 31, 2017 and March 31, 2017 (amounts in thousands). As of December 31, 2017 and March 31, 2017 , the carrying amounts of the Company's senior and junior subordinated convertible debt have been reduced by debt issuance costs of $35.2 million and $38.3 million , respectively. December 31, 2017 March 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value 2017 Senior Debt $ 1,424,169 $ 2,436,742 $ 1,384,914 $ 2,106,225 2015 Senior Debt $ 1,297,605 $ 2,952,993 $ 1,261,787 $ 2,481,708 2017 Junior Debt $ 324,528 $ 814,329 $ 262,298 $ 586,609 2007 Junior Debt $ — $ — $ 49,952 $ 445,142

Other Financial Statements De38

Other Financial Statements Details (Tables)	9 Months Ended
	Dec. 31, 2017
Accounts Receivable, Net [Abstract]
Accounts receivable schedule	Accounts receivable consists of the following (amounts in thousands): December 31, 2017 March 31, 2017 Trade accounts receivable $ 547,572 $ 473,238 Other 7,682 7,219 Total accounts receivable, gross 555,254 480,457 Less allowance for doubtful accounts 2,119 2,084 Total accounts receivable, net $ 553,135 $ 478,373
Components of inventories	The components of inventories consist of the following (amounts in thousands): December 31, 2017 March 31, 2017 Raw materials $ 22,488 $ 14,430 Work in process 309,811 268,281 Finished goods 154,766 134,491 Total inventories $ 487,065 $ 417,202
Schedule of property, plant and equipment	Property, plant and equipment consists of the following (amounts in thousands): December 31, 2017 March 31, 2017 Land $ 73,447 $ 73,447 Building and building improvements 506,037 499,668 Machinery and equipment 1,911,200 1,774,920 Projects in process 115,006 104,318 Total property, plant and equipment, gross 2,605,690 2,452,353 Less accumulated depreciation and amortization 1,850,910 1,769,015 Total property, plant and equipment, net $ 754,780 $ 683,338

Intangible Assets and Goodwil39

Intangible Assets and Goodwill (Tables)	9 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets	Intangible assets consist of the following (amounts in thousands): December 31, 2017 Gross Amount Accumulated Amortization Net Amount Core and developed technology $ 1,936,956 $ (587,415 ) $ 1,349,541 Customer-related 716,945 (312,851 ) 404,094 Trademarks and trade names 11,700 (11,185 ) 515 In-process research and development 29,379 — 29,379 Distribution rights 5,578 (5,379 ) 199 Other 1,449 (609 ) 840 Total $ 2,702,007 $ (917,439 ) $ 1,784,568 March 31, 2017 Gross Amount Accumulated Amortization Net Amount Core and developed technology $ 1,932,329 $ (419,468 ) $ 1,512,861 Customer-related 716,945 (123,616 ) 593,329 Trademarks and trade names 11,700 (9,636 ) 2,064 In-process research and development 38,511 — 38,511 Distribution rights 5,578 (5,346 ) 232 Other 1,449 (354 ) 1,095 Total $ 2,706,512 $ (558,420 ) $ 2,148,092
Projected amortization expense	The following is an expected amortization schedule for the intangible assets for the remainder of fiscal 2018 through fiscal 2022 , absent any future acquisitions or impairment charges (amounts in thousands): Fiscal Year Ending March 31, Projected Amortization Expense 2018 $122,252 2019 361,682 2020 313,484 2021 257,430 2022 190,429
Goodwill activity	The following shows the goodwill balance as of December 31, 2017 and March 31, 2017 by segment (amounts in thousands): Semiconductor Products Reporting Unit Technology Licensing Reporting Unit Goodwill $ 2,279,809 $ 19,200

Debt and Credit Facility (Table

Debt and Credit Facility (Tables)	9 Months Ended
	Dec. 31, 2017
Convertible Debt [Abstract]
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments	Debt obligations included in the condensed consolidated balance sheets consisted of the following (in millions): Coupon Interest Rate Effective Interest Rate Fair Value of Liability Component at Issuance (1) December 31, 2017 March 31, 2017 Senior Indebtedness Credit Facility $ — $ — Senior Subordinated Convertible Debt - Principal Outstanding 2017 Senior Debt, maturing February 15, 2027 (2017 Senior Debt) 1.625% 6.0% $1,396.3 $ 2,070.0 $ 2,070.0 2015 Senior Debt, maturing February 15, 2025 (2015 Senior Debt) 1.625% 5.9% 1,160.1 1,725.0 1,725.0 Junior Subordinated Convertible Debt - Principal Outstanding 2017 Junior Debt, maturing February 15, 2037 (2017 Junior Debt) 2.250% 7.4% 321.1 686.3 575.0 2007 Junior Debt, maturing December 15, 2037 (2007 Junior Debt) 2.125% 9.1% — — 143.8 Total Convertible Debt 4,481.3 4,513.8 Gross long-term debt including current maturities 4,481.3 4,513.8 Less: Debt discount (2) (1,399.8 ) (1,516.5 ) Less: Debt issuance costs (3) (41.9 ) (46.8 ) Net long-term debt including current maturities 3,039.6 2,950.5 Less: Current maturities (4) — (50.0 ) Net long-term debt $ 3,039.6 $ 2,900.5 (1) As each of the convertible instruments may be settled in cash upon conversion, for accounting purposes, they were bifurcated into a liability component and an equity component, which are both initially recorded at fair value. The amount allocated to the equity component is the difference between the principal value of the instrument and the fair value of the liability component at issuance. The resulting debt discount is being amortized to interest expense at the respective effective interest rate over the contractual term of the debt. (2) The unamortized discount includes the following (in millions): December 31, March 31, 2017 2017 2017 Senior Debt $ (629.3 ) $ (667.5 ) 2015 Senior Debt (412.1 ) (446.6 ) 2017 Junior Debt (358.4 ) (309.3 ) 2007 Junior Debt — (93.1 ) Total unamortized discount $ (1,399.8 ) $ (1,516.5 ) (3) Debt issuance costs include the following (in millions): December 31, March 31, 2017 2017 Senior Credit Facility $ (6.7 ) $ (8.5 ) 2017 Senior Debt (16.5 ) (17.6 ) 2015 Senior Debt (15.3 ) (16.6 ) 2017 Junior Debt (3.4 ) (3.4 ) 2007 Junior Debt — (0.7 ) Total debt issuance costs $ (41.9 ) $ (46.8 ) (4) Current maturities include the full balance of the 2007 Junior Debt as of March 31, 2017.
Schedule of Unamortized Discount and Debt Issuance Costs	(2) The unamortized discount includes the following (in millions): December 31, March 31, 2017 2017 2017 Senior Debt $ (629.3 ) $ (667.5 ) 2015 Senior Debt (412.1 ) (446.6 ) 2017 Junior Debt (358.4 ) (309.3 ) 2007 Junior Debt — (93.1 ) Total unamortized discount $ (1,399.8 ) $ (1,516.5 ) (3) Debt issuance costs include the following (in millions): December 31, March 31, 2017 2017 Senior Credit Facility $ (6.7 ) $ (8.5 ) 2017 Senior Debt (16.5 ) (17.6 ) 2015 Senior Debt (15.3 ) (16.6 ) 2017 Junior Debt (3.4 ) (3.4 ) 2007 Junior Debt — (0.7 ) Total debt issuance costs $ (41.9 ) $ (46.8 ) (4) Current maturities include the full balance of the 2007 Junior Debt as of March 31, 2017.
Schedule of Convertible Debt	The following table sets forth the applicable Conversion Rates adjusted for dividends declared since issuance of such series of Convertible Debt and the applicable Incremental Share Factors and Maximum Conversion Rates as adjusted for dividends paid since the applicable issuance date: Dividend adjusted rates as of December 31, 2017 Conversion Rate, adjusted Approximate Conversion Price, adjusted Incremental Share Factor, adjusted Maximum Conversion Rate, adjusted 2017 Senior Debt 10.0722 $ 99.28 5.0361 14.3529 2015 Senior Debt 15.7069 $ 63.67 7.8534 21.9896 2017 Junior Debt 10.2521 $ 97.54 5.1261 14.3529 The following is the weighted average conversion price per share used in calculating the dilutive effect (See Note 13 for details on the convertible debt): Three Months Ended Nine Months Ended December 31, December 31, 2017 2016 2017 2016 2007 Junior Debt $ 23.49 $ 23.93 $ 23.59 $ 24.08 2015 Senior Debt $ 63.80 $ 65.00 $ 64.07 $ 65.40 2017 Senior Debt $ 99.50 $ — $ 99.92 $ — 2017 Junior Debt $ 97.75 $ — $ 98.16 $ —
Schedule of Interest Expense	Interest expense related to convertible debt includes the following (in millions): Three Months Ended Nine Months Ended December 31, 2017 2016 2017 2016 Debt issuance amortization $ 0.9 $ 0.5 $ 2.7 $ 1.3 Amortization of debt discount - non cash interest expense 26.7 12.5 79.0 36.9 Coupon interest expense 19.3 10.1 58.1 30.3 Total $ 46.9 $ 23.1 $ 139.8 $ 68.5

Pension Plans (Tables)

Pension Plans (Tables)	9 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Schedule of net benefit costs	The aggregate net pension expense relating to these two plans are as follows (amounts in thousands): Three Months Ended Nine Months Ended December 31, December 31, 2017 2016 2017 2016 Service costs $ 390 $ 327 $ 1,131 $ 1,054 Interest costs 253 214 742 698 Amortization of actuarial loss 214 — 630 — Settlements and curtailments — 354 (36 ) 585 Net pension period cost $ 857 $ 895 $ 2,467 $ 2,337

Comprehensive (Loss) Income (Ta

Comprehensive (Loss) Income (Tables)	9 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of accumulated other comprehensive income (loss)	The following table presents the changes in the components of accumulated other comprehensive (loss) income (AOCI), net of tax, for the nine months ended December 31, 2017 (amounts in thousands): Unrealized holding gains (losses) available-for-sale securities Defined benefit pension plans Foreign Currency Total Accumulated other comprehensive income (loss) at March 31, 2017 $ 312 $ (5,263 ) $ (9,427 ) $ (14,378 ) Other comprehensive loss before reclassifications (6,161 ) (2,284 ) — (8,445 ) Amounts reclassified from accumulated other comprehensive loss — 630 — 630 Net other comprehensive loss (6,161 ) (1,654 ) — (7,815 ) Accumulated other comprehensive loss at December 31, 2017 $ (5,849 ) $ (6,917 ) $ (9,427 ) $ (22,193 )
Reclassification out of accumulated other comprehensive income	The table below details where reclassifications of realized transactions out of AOCI are recorded on the condensed consolidated statements of operations (amounts in thousands): Three Months Ended Nine Months Ended December 31, December 31, Description of AOCI Component 2017 2016 2017 2016 Related Statement of Income Line Unrealized losses on available-for-sale securities $ — $ (1,433 ) $ — $ (1,522 ) Other income (loss) Amortization of actuarial loss (214 ) — (630 ) — Other income (loss) Reclassification of realized transactions, net of taxes $ (214 ) $ (1,433 ) $ (630 ) $ (1,522 ) Net income

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Dec. 31, 2017
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, 2017 2016 2017 2016 Cost of sales (1) $ 3,494 $ 3,468 $ 10,587 $ 15,465 Research and development 10,921 9,881 31,797 37,569 Selling, general and administrative 9,588 8,771 27,637 53,055 Pre-tax effect of share-based compensation 24,003 22,120 70,021 106,089 Income tax benefit (2) 6,604 7,376 21,878 36,622 Net income effect of share-based compensation $ 17,399 $ 14,744 $ 48,143 $ 69,467 (1) During the three and nine months ended December 31, 2017 , $3.1 million and $8.9 million , respectively, of share-based compensation expense was capitalized to inventory and $3.5 million and $10.6 million , respectively, of previously capitalized share-based compensation expense in inventory was sold. During the three and nine months ended December 31, 2016 , $2.8 million and $8.3 million , respectively, of share-based compensation expense was capitalized to inventory. The amount of share-based compensation included in cost of sales during the three months ended December 31, 2016 included $3.5 million of previously capitalized share-based compensation expense in inventory that was sold. The amount of share-based compensation included in cost of sales during the nine months ended December 31, 2016 included $11.3 million of previously capitalized share-based compensation expense in inventory that was sold and $4.2 million of share-based compensation expense related to the Company's acquisition of Atmel that was not previously capitalized to inventory. (2) Amounts exclude excess tax benefits related to share-based compensation of $5.7 million and $19.8 million , respectively, for the three and nine months ended December 31, 2017 and $6.1 million and $18.6 million , respectively, for the three and nine months ended December 31, 2016 .

Net (Loss) Income Per Common 44

Net (Loss) Income Per Common Share From Continuing Operations (Tables)	9 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of earnings per share, basic and diluted	The following table sets forth the computation of basic and diluted net (loss) income per common share from continuing operations (in thousands, except per share amounts): Three Months Ended Nine Months Ended December 31, December 31, 2017 2016 2017 2016 Net (loss) income from continuing operations $ (251,086 ) $ 107,335 $ 108,657 $ 33,684 Weighted average common shares outstanding 234,106 216,210 232,278 215,360 Dilutive effect of stock options and RSUs — 4,330 4,460 4,317 Dilutive effect of 2007 Junior debt — 14,884 1,735 13,674 Dilutive effect of 2015 Senior debt — — 9,551 — Dilutive effect of 2017 Senior debt — — — — Dilutive effect of 2017 Junior debt — — — — Weighted average common and potential common shares outstanding 234,106 235,424 248,024 233,351 Basic net (loss) income per common share from continuing operations $ (1.07 ) $ 0.50 $ 0.47 $ 0.16 Diluted net (loss) income per common share from continuing operations $ (1.07 ) $ 0.46 $ 0.44 $ 0.14
Schedule of Convertible Debt	The following table sets forth the applicable Conversion Rates adjusted for dividends declared since issuance of such series of Convertible Debt and the applicable Incremental Share Factors and Maximum Conversion Rates as adjusted for dividends paid since the applicable issuance date: Dividend adjusted rates as of December 31, 2017 Conversion Rate, adjusted Approximate Conversion Price, adjusted Incremental Share Factor, adjusted Maximum Conversion Rate, adjusted 2017 Senior Debt 10.0722 $ 99.28 5.0361 14.3529 2015 Senior Debt 15.7069 $ 63.67 7.8534 21.9896 2017 Junior Debt 10.2521 $ 97.54 5.1261 14.3529 The following is the weighted average conversion price per share used in calculating the dilutive effect (See Note 13 for details on the convertible debt): Three Months Ended Nine Months Ended December 31, December 31, 2017 2016 2017 2016 2007 Junior Debt $ 23.49 $ 23.93 $ 23.59 $ 24.08 2015 Senior Debt $ 63.80 $ 65.00 $ 64.07 $ 65.40 2017 Senior Debt $ 99.50 $ — $ 99.92 $ — 2017 Junior Debt $ 97.75 $ — $ 98.16 $ —

Business Acquisitions (Narrativ

Business Acquisitions (Narrative) (Details) $ in Thousands, shares in Millions	Apr. 04, 2016USD ($)shares
Business Acquisition [Line Items]
Net deferred tax liability for future amortization expense of acquired intangible assets	$ 178,100
Atmel Corporation
Business Acquisition [Line Items]
Cash paid for shares	$ 2,980,000
Shares issued as part of acquisition | shares	10.1
Value of shares issued as part of acquisition	$ 486,100
Transaction and other fees incurred in transaction	14,900
Non cash consideration of certain share-based payment awards	7,500
Total consideration transferred	3,470,000
Liabilities assumed	653,058
Payments to acquire businesses portion funded by foreign subsidiaries cash balances	2,040,000
Payments to acquire businesses portion funded by additional line of credit borrowings	$ 940,000

Business Acquisitions (Schedule

Business Acquisitions (Schedule of Purchase Price Allocation) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017	Apr. 04, 2016
Assets acquired
Goodwill	$ 2,299,009	$ 2,299,009
Atmel Corporation
Assets acquired
Cash and cash equivalents			$ 230,266
Accounts receivable			141,359
Inventories			335,163
Prepaid expenses and other current assets			28,360
Assets held for sale			32,006
Property, plant and equipment, net			129,884
Goodwill			1,286,371
Purchased intangible assets			1,888,392
Long-term deferred tax assets			46,700
Other assets			7,535
Total assets acquired			4,126,036
Liabilities assumed
Accounts payable			(55,686)
Other current liabilities			(120,955)
Long-term line of credit			(192,000)
Deferred tax liabilities			(27,552)
Long-term income tax payable			(115,177)
Other long-term liabilities			(141,688)
Total liabilities assumed			(653,058)
Purchase price allocated			$ 3,472,978

Business Acquisitions (Schedu47

Business Acquisitions (Schedule of Purchased Intangible Assets) (Details) - Atmel Corporation $ in Thousands	Apr. 04, 2016USD ($)
Business Acquisition [Line Items]
Useful life	9 years
Purchased intangible assets	$ 1,888,392
Core/developed technology
Business Acquisition [Line Items]
Useful life	11 years
Purchased intangible assets	$ 1,074,987
Customer-related
Business Acquisition [Line Items]
Useful life	6 years
Purchased intangible assets	$ 630,600
Backlog
Business Acquisition [Line Items]
Useful life	1 year
Purchased intangible assets	$ 40,300
Other
Business Acquisition [Line Items]
Useful life	5 years
Purchased intangible assets	$ 1,805
In-process technology
Business Acquisition [Line Items]
Indefinite-lived Intangible Assets Acquired	$ 140,700

Discontinued Operations (Detail

Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Net sales		$ 923		$ 18,334
Cost of sales		478		15,841
Operating expenses		1,279		10,650
Gain on Sale		643		643
Income tax benefit	$ 0	(31)	$ 0	(1,561)
Net loss from discontinued operations	$ 0	$ (160)	$ 0	$ (5,953)

Special Charges and Other, Ne49

Special Charges and Other, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Other Nonrecurring (Income) Expense [Abstract]
Employee separation costs	$ 90	$ 6,525	$ 1,477	$ 35,346
Gain on sale of assets	0	0	(4,447)	0
Impairment charges	99	8,084	199	10,045
Contract exit costs	(97)	4,954	20,057	5,294
Other	104	1,381	26	1,837
Special charges and other, net	$ 196	$ 20,944	$ 17,312	$ 52,522

Special Charges and Other, Ne50

Special Charges and Other, Net Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		45 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Employee separation costs	$ 90			$ 6,525	$ 1,477	$ 35,346
Contract exit costs	$ (97)			4,954	20,057	5,294
Supply commitment, period	10 years
Gain on sale of assets	$ 0			0	4,447	0
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			$ 40,225		40,225
Charges					21,534
Payments					(11,845)
Non-cash - Other					582
Foreign exchange gains					272
Restructuring reserve, ending balance	$ 50,768				50,768		$ 50,768
Contract Termination
Restructuring Cost and Reserve [Line Items]
Incurred cost		$ 19,500
Contract termination fee, period	5 years
Employee Severance
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			5,474		5,474
Charges					1,477
Payments					(4,755)
Non-cash - Other					(287)
Foreign exchange gains					272
Restructuring reserve, ending balance	$ 2,181				2,181		2,181
Exit Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			34,751		34,751
Charges					20,057
Payments					(7,090)
Non-cash - Other					869
Foreign exchange gains					0
Restructuring reserve, ending balance	48,587				48,587		48,587
Accrued Liabilities
Restructuring Reserve [Roll Forward]
Current	14,042				14,042		14,042
Other Noncurrent Liabilities
Restructuring Reserve [Roll Forward]
Non-current	36,726				36,726		36,726
Semiconductor products
Restructuring Cost and Reserve [Line Items]
Employee separation costs	100			6,500	1,500	35,300	52,600
Contract exit costs	$ (100)			$ 5,000	$ 20,100	$ 5,300	$ 64,800
San Jose Facility | Micrel Incorporated
Restructuring Cost and Reserve [Line Items]
Proceeds from sale of property, plant, and equipment			10,000
Gain on sale of assets			$ 4,400

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Segment reporting information [Line Items]
Net Sales	$ 994,205	$ 834,366	$ 2,978,485	$ 2,505,141
Gross Profit	607,059	465,259	1,805,592	1,224,370
Semiconductor products
Segment reporting information [Line Items]
Net Sales	966,678	810,532	2,900,145	2,437,049
Gross Profit	579,532	441,425	1,727,252	1,156,278
Technology licensing
Segment reporting information [Line Items]
Net Sales	27,527	23,834	78,340	68,092
Gross Profit	$ 27,527	$ 23,834	$ 78,340	$ 68,092

Investments Summary of Availabl

Investments Summary of Available for Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Summary of available-for-sale securities [Line Items]
Adjusted Cost	$ 1,318,498	$ 500,973
Available-for-sale, gross unrealized gain	1,758	978
Available-for-sale, gross unrealized loss	(7,350)	(406)
Estimated Fair Value	1,312,906	501,545
Government agency bonds
Summary of available-for-sale securities [Line Items]
Adjusted Cost	815,940	227,089
Available-for-sale, gross unrealized gain	0	3
Available-for-sale, gross unrealized loss	(5,809)	(227)
Estimated Fair Value	810,131	226,865
Municipal bonds - tax-exempt
Summary of available-for-sale securities [Line Items]
Adjusted Cost		55,289
Available-for-sale, gross unrealized gain		0
Available-for-sale, gross unrealized loss		(10)
Estimated Fair Value		55,279
Municipal bonds - taxable
Summary of available-for-sale securities [Line Items]
Adjusted Cost	10,000	10,000
Available-for-sale, gross unrealized gain	0	43
Available-for-sale, gross unrealized loss	(57)	0
Estimated Fair Value	9,943	10,043
Corporate bonds and debt
Summary of available-for-sale securities [Line Items]
Adjusted Cost	491,851	207,888
Available-for-sale, gross unrealized gain	0	53
Available-for-sale, gross unrealized loss	(1,484)	(169)
Estimated Fair Value	490,367	207,772
Marketable equity securities
Summary of available-for-sale securities [Line Items]
Adjusted Cost	707	707
Available-for-sale, gross unrealized gain	1,758	879
Available-for-sale, gross unrealized loss	0	0
Estimated Fair Value	$ 2,465	$ 1,586

Investments AFS (Details)

Investments AFS (Details) - USD ($) $ in Thousands	9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Investments [Abstract]
Short-term Investments	$ 427,514		$ 394,088
Long-term investments	885,392		$ 107,457
Available-for-sale securities, gross realized gains (losses), sale proceeds	$ 0	$ 470,200

Investments AFS, Continuous Unr

Investments AFS, Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Fair value of available-for-sale securities in a continuous unrealized loss position, less than twelve months	$ 1,247,329	$ 384,974
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, less than twelve months	(7,156)	(406)
Fair value of available-for-sale securities in a continuous unrealized loss position, greater than twelve months	19,806	0
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, greater than twelve months	(194)	0
Fair value of available-for-sale securities in a continuous unrealized loss position	1,267,135	384,974
Accumulated loss, available-for-sale securities in a continuous unrealized loss position	(7,350)	(406)
Government agency bonds
Schedule of Available-for-sale Securities [Line Items]
Fair value of available-for-sale securities in a continuous unrealized loss position, less than twelve months	790,325	196,875
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, less than twelve months	(5,615)	(227)
Fair value of available-for-sale securities in a continuous unrealized loss position, greater than twelve months	19,806	0
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, greater than twelve months	(194)	0
Fair value of available-for-sale securities in a continuous unrealized loss position	810,131	196,875
Accumulated loss, available-for-sale securities in a continuous unrealized loss position	(5,809)	(227)
Municipal bonds - taxable
Schedule of Available-for-sale Securities [Line Items]
Fair value of available-for-sale securities in a continuous unrealized loss position, less than twelve months	9,943
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, less than twelve months	(57)
Fair value of available-for-sale securities in a continuous unrealized loss position, greater than twelve months	0
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, greater than twelve months	0
Fair value of available-for-sale securities in a continuous unrealized loss position	9,943
Accumulated loss, available-for-sale securities in a continuous unrealized loss position	(57)
Municipal bonds - tax-exempt
Schedule of Available-for-sale Securities [Line Items]
Fair value of available-for-sale securities in a continuous unrealized loss position, less than twelve months		55,279
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, less than twelve months		(10)
Fair value of available-for-sale securities in a continuous unrealized loss position, greater than twelve months		0
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, greater than twelve months		0
Fair value of available-for-sale securities in a continuous unrealized loss position		55,279
Accumulated loss, available-for-sale securities in a continuous unrealized loss position		(10)
Corporate bonds and debt
Schedule of Available-for-sale Securities [Line Items]
Fair value of available-for-sale securities in a continuous unrealized loss position, less than twelve months	447,061	132,820
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, less than twelve months	(1,484)	(169)
Fair value of available-for-sale securities in a continuous unrealized loss position, greater than twelve months	0	0
Accumulated loss, available-for-sale securities in a continuous unrealized loss position, greater than twelve months	0	0
Fair value of available-for-sale securities in a continuous unrealized loss position	447,061	132,820
Accumulated loss, available-for-sale securities in a continuous unrealized loss position	$ (1,484)	$ (169)

Investments, AFS Maturities (De

Investments, AFS Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	$ 1,318,498	$ 500,973
Available-for-sale, gross unrealized gain	1,758	978
Available-for-sale, gross unrealized loss	(7,350)	(406)
Estimated Fair Value	1,312,906	501,545
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	707	707
Available-for-sale, gross unrealized gain	1,758	879
Available-for-sale, gross unrealized loss	0	0
Estimated Fair Value	2,465	$ 1,586
Due in one year or less
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	425,436
Available-for-sale, gross unrealized gain	0
Available-for-sale, gross unrealized loss	(387)
Estimated Fair Value	425,049
Due after one year and through five years
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	892,355
Available-for-sale, gross unrealized gain	0
Available-for-sale, gross unrealized loss	(6,963)
Estimated Fair Value	885,392
Due after five years and through ten years
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	0
Available-for-sale, gross unrealized gain	0
Available-for-sale, gross unrealized loss	0
Estimated Fair Value	0
Total
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	1,317,791
Available-for-sale, gross unrealized gain	0
Available-for-sale, gross unrealized loss	(7,350)
Estimated Fair Value	$ 1,310,441

Fair Value Measurements, Measur

Fair Value Measurements, Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	$ 1,312,906	$ 501,545
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	1,984,985	1,410,229
Marketable equity securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	2,465	1,586
Corporate bonds and debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	490,367	207,772
Government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	810,131	226,865
Municipal bonds - tax-exempt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value		55,279
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	110,669	345,401
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	1,874,316	1,064,828
Cash and Cash Equivalents | Money market mutual funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	108,204	343,815
Cash and Cash Equivalents | Deposit accounts | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	563,875	564,869
Cash and Cash Equivalents | Fair Value, Inputs, Level 1 | Money market mutual funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	108,204	343,815
Cash and Cash Equivalents | Fair Value, Inputs, Level 1 | Deposit accounts | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	0	0
Cash and Cash Equivalents | Fair Value, Inputs, Level 2 | Money market mutual funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	0	0
Cash and Cash Equivalents | Fair Value, Inputs, Level 2 | Deposit accounts | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	563,875	564,869
Short-term Investments | Marketable equity securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	2,465	1,586
Short-term Investments | Corporate bonds and debt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	288,224	165,207
Short-term Investments | Government agency bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	136,825	161,973
Short-term Investments | Municipal bonds - tax-exempt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value		55,279
Short-term Investments | Municipal bonds - taxable | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value		10,043
Short-term Investments | Fair Value, Inputs, Level 1 | Marketable equity securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	2,465	1,586
Short-term Investments | Fair Value, Inputs, Level 1 | Corporate bonds and debt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	0	0
Short-term Investments | Fair Value, Inputs, Level 1 | Government agency bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	0	0
Short-term Investments | Fair Value, Inputs, Level 1 | Municipal bonds - tax-exempt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value		0
Short-term Investments | Fair Value, Inputs, Level 1 | Municipal bonds - taxable | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value		0
Short-term Investments | Fair Value, Inputs, Level 2 | Marketable equity securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	0	0
Short-term Investments | Fair Value, Inputs, Level 2 | Corporate bonds and debt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	288,224	165,207
Short-term Investments | Fair Value, Inputs, Level 2 | Government agency bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	136,825	161,973
Short-term Investments | Fair Value, Inputs, Level 2 | Municipal bonds - tax-exempt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value		55,279
Short-term Investments | Fair Value, Inputs, Level 2 | Municipal bonds - taxable | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value		10,043
Other Long-term Investments | Corporate bonds and debt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	202,143	42,565
Other Long-term Investments | Government agency bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	673,306	64,892
Other Long-term Investments | Municipal bonds - taxable | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	9,943
Other Long-term Investments | Fair Value, Inputs, Level 1 | Corporate bonds and debt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	0	0
Other Long-term Investments | Fair Value, Inputs, Level 1 | Government agency bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	0	0
Other Long-term Investments | Fair Value, Inputs, Level 1 | Municipal bonds - taxable | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	0
Other Long-term Investments | Fair Value, Inputs, Level 2 | Corporate bonds and debt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	202,143	42,565
Other Long-term Investments | Fair Value, Inputs, Level 2 | Government agency bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	673,306	$ 64,892
Other Long-term Investments | Fair Value, Inputs, Level 2 | Municipal bonds - taxable | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale, estimated fair value	$ 9,943

Fair Value of Financial Instr57

Fair Value of Financial Instruments (Narrative details) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Debt issuance costs	$ 35.2	$ 38.3

Fair Value of Financial Instr58

Fair Value of Financial Instruments (Schedule of carrying amounts and fair values) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Carrying Value | 2017 Senior Subordinated Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	$ 1,424,169	$ 1,384,914
Carrying Value | 2015 Senior Subordinated Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	1,297,605	1,261,787
Carrying Value | 2017 Junior Subordinated Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	324,528	262,298
Carrying Value | 2007 Junior Subordinated Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	0	49,952
Estimate of Fair Value Measurement | 2017 Senior Subordinated Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	2,436,742	2,106,225
Estimate of Fair Value Measurement | 2015 Senior Subordinated Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	2,952,993	2,481,708
Estimate of Fair Value Measurement | 2017 Junior Subordinated Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	814,329	586,609
Estimate of Fair Value Measurement | 2007 Junior Subordinated Convertible Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure for subordinated convertible debentures	$ 0	$ 445,142

Other Financial Statements De59

Other Financial Statements Details Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 555,254	$ 480,457
Less allowance for doubtful accounts	2,119	2,084
Accounts receivable, net	553,135	478,373
Trade Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	547,572	473,238
Other Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 7,682	$ 7,219

Other Financial Statements De60

Other Financial Statements Details Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Accounts Receivable, Net [Abstract]
Raw materials	$ 22,488	$ 14,430
Work in process	309,811	268,281
Finished goods	154,766	134,491
Total inventories	$ 487,065	$ 417,202

Other Financial Statements De61

Other Financial Statements Details Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 2,605,690		$ 2,605,690		$ 2,452,353
Less accumulated depreciation and amortization	1,850,910		1,850,910		1,769,015
Property, plant and equipment, net	754,780		754,780		683,338
Depreciation	32,000	$ 29,700	90,900	$ 90,300
Land
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	73,447		73,447		73,447
Buildings and building improvements
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	506,037		506,037		499,668
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	1,911,200		1,911,200		1,774,920
Projects in progress
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 115,006		$ 115,006		$ 104,318

Intangible Assets, by Major Cla

Intangible Assets, by Major Class (Details) - USD ($) $ in Thousands	Apr. 04, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount		$ 2,702,007		$ 2,702,007		$ 2,706,512
Accumulated Amortization		(917,439)		(917,439)		(558,420)
Net Amount		1,784,568		1,784,568		2,148,092
In-process technology reaching technological feasibility and reclassified				8,900
Amortization of Intangible Assets		122,600	$ 85,200	368,100	$ 250,600
Impairment of Intangible Assets			8,200	252	10,226
Projected Amortization Expense
2,018		122,252		122,252
2,019		361,682		361,682
2,020		313,484		313,484
2,021		257,430		257,430
2,022		190,429		190,429
Core and developed technology
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount		1,936,956		1,936,956		1,932,329
Accumulated Amortization		(587,415)		(587,415)		(419,468)
Net Amount		1,349,541		1,349,541		1,512,861
Customer-related
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount		716,945		716,945		716,945
Accumulated Amortization		(312,851)		(312,851)		(123,616)
Net Amount		404,094		404,094		593,329
Trademarks and trade names
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount		11,700		11,700		11,700
Accumulated Amortization		(11,185)		(11,185)		(9,636)
Net Amount		515		515		2,064
In-process technology
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount		29,379		29,379		38,511
Accumulated Amortization		0		0		0
Net Amount		29,379		29,379		38,511
Distribution rights
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount		5,578		5,578		5,578
Accumulated Amortization		(5,379)		(5,379)		(5,346)
Net Amount		199		199		232
Other
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount		1,449		1,449		1,449
Accumulated Amortization		(609)		(609)		(354)
Net Amount		840		$ 840		$ 1,095
Minimum
Finite-Lived Intangible Assets, Net [Abstract]
Useful life				1 year
Maximum
Finite-Lived Intangible Assets, Net [Abstract]
Useful life				15 years
Atmel Corporation
Finite-Lived Intangible Assets, Net [Abstract]
Useful life	9 years
Purchased intangible assets	$ 1,888,392
Atmel Corporation | Core and developed technology
Finite-Lived Intangible Assets, Net [Abstract]
Useful life	11 years
Purchased intangible assets	$ 1,074,987
Atmel Corporation | Other
Finite-Lived Intangible Assets, Net [Abstract]
Useful life	5 years
Purchased intangible assets	$ 1,805
Cost of Sales
Finite-Lived Intangible Assets, Net [Abstract]
Amortization of Intangible Assets		1,500	900	$ 4,900	2,800
Operating Expense
Finite-Lived Intangible Assets, Net [Abstract]
Amortization of Intangible Assets		$ 121,100	$ 84,300	$ 363,200	$ 247,800

Goodwill by Reporting Segment (

Goodwill by Reporting Segment (Details) $ in Thousands	12 Months Ended
	Mar. 31, 2017USD ($)unit	Dec. 31, 2017USD ($)
Goodwill By Reporting Segment [Line Items]
Number of reporting units | unit	2
Goodwill [Roll Forward]
Goodwill	$ 2,299,009	$ 2,299,009
Semiconductor products
Goodwill [Roll Forward]
Goodwill	2,279,809	2,279,809
Technology licensing
Goodwill [Roll Forward]
Goodwill	$ 19,200	$ 19,200

Income Tax (Narrative) (Details

Income Tax (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate (benefit)	227.70%	(28.50%)	(80.20%)	(87.30%)
Income Tax [Line Items]
Tax Cuts And Jobs Act Of 2017, transition tax for accumulated foreign earnings			$ 443.2
Tax Cuts And Jobs Act Of 2017, provisional income tax expense (benefit), effect of change on earnings per share, diluted			$ (1.79)
Tax Cuts And Jobs Act Of 2017, provisional income tax expense (benefit)			$ 627.7
Tax Cuts And Jobs Act Of 2017,change in tax rate, deferred tax liability, provisional income tax expense			(5.5)
Tax Cuts And Jobs Act Of 2017, transition tax for accumulated foreign earnings			622.2
Tax Cuts And Jobs Act Of 2017, change in tax rate, deferred tax asset			142.6
Tax Cuts And Jobs Act Of 2017, provisional income tax expense (benefit), deferred tax assets, tax credit carryforwards, foreign			$ (36.4)
Scenario, Forecast
Income Tax [Line Items]
Effective income tax rate reconciliation, at Federal statutory income tax rate					31.50%

Debt and Credit Facility Debt O

Debt and Credit Facility Debt Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017	Feb. 28, 2017	Feb. 28, 2015
Debt Instrument [Line Items]
Credit Facility		$ 0
Long-term debt, gross	$ 4,481,300	4,513,800
Total Convertible Debt	4,481,300	4,513,800
Less: Debt discount	(1,399,800)	(1,516,500)
Less: Debt issuance costs	(41,900)	(46,800)	$ (33,700)
Net long-term debt including current maturities	3,039,600	2,950,500
Current portion of long-term debt	0	(49,952)
Net long-term debt	3,039,623	2,900,524
December 2015 Amended Credit Facility with Maturity Dates of June 2018 and February 2020
Debt Instrument [Line Items]
Credit Facility	0	0
Less: Debt issuance costs	$ (6,700)	(8,500)
2017 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Coupon Interest Rate	1.625%
Effective Interest Rate	6.00%
Fair Value of Liability Component at Issuance (1)	$ 1,396,300
Long-term debt, gross	2,070,000	2,070,000
Less: Debt discount	(629,300)	(667,500)
Less: Debt issuance costs	$ (16,500)	(17,600)
2015 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Coupon Interest Rate	1.625%
Effective Interest Rate	5.90%
Fair Value of Liability Component at Issuance (1)	$ 1,160,100
Long-term debt, gross	1,725,000	1,725,000
Less: Debt discount	(412,100)	(446,600)
Less: Debt issuance costs	$ (15,300)	(16,600)
2017 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Coupon Interest Rate	2.25%
Effective Interest Rate	7.40%
Fair Value of Liability Component at Issuance (1)	$ 321,100
Long-term debt, gross	686,300	575,000
Less: Debt discount	(358,400)	(309,300)
Less: Debt issuance costs	$ (3,400)	(3,400)		$ (30,300)
2007 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Coupon Interest Rate	2.125%
Effective Interest Rate	9.10%
Fair Value of Liability Component at Issuance (1)	$ 0
Long-term debt, gross	0	143,800
Less: Debt discount	0	(93,100)
Less: Debt issuance costs	$ 0	$ (700)

Debt and Credit Facility Compon

Debt and Credit Facility Components (Details) - USD ($) $ in Millions	Dec. 31, 2017	Mar. 31, 2017	Feb. 28, 2017	Feb. 28, 2015
Debt Instrument [Line Items]
Amount of unamortized debt discount of debentures	$ (1,399.8)	$ (1,516.5)
Debt issuance costs	(41.9)	(46.8)	$ (33.7)
December 2015 Amended Credit Facility with Maturity Dates of June 2018 and February 2020
Debt Instrument [Line Items]
Debt issuance costs	(6.7)	(8.5)
2017 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Amount of unamortized debt discount of debentures	(629.3)	(667.5)
Debt issuance costs	(16.5)	(17.6)
2015 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Amount of unamortized debt discount of debentures	(412.1)	(446.6)
Debt issuance costs	(15.3)	(16.6)
2017 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Amount of unamortized debt discount of debentures	(358.4)	(309.3)
Debt issuance costs	(3.4)	(3.4)		$ (30.3)
2007 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Amount of unamortized debt discount of debentures	0	(93.1)
Debt issuance costs	$ 0	$ (0.7)

Debt and Credit Facility Conver

Debt and Credit Facility Conversion Features (Details) $ in Millions	3 Months Ended	9 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2017day
2015 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible, if-converted value in excess of principal | $	$ 1,108.8
2007 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible, threshold percentage of stock price trigger		130.00%
Convertible Debt
Debt Instrument [Line Items]
Debt Instrument, redemption price, percentage		100.00%
Convertible Debt | Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Debt instrument, convertible, threshold percentage of stock price trigger		130.00%
Debt instrument, convertible, threshold trading days		20
Debt instrument, convertible, threshold consecutive trading days		30
Convertible Debt | Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Debt instrument, convertible, threshold percentage of stock price trigger		98.00%
Debt instrument, convertible, threshold trading days		5
Debt instrument, convertible, threshold consecutive trading days		10

Debt and Credit Facility Conv68

Debt and Credit Facility Convertible Debt (Details)	9 Months Ended
	Dec. 31, 2017$ / shares
2017 Senior Subordinated Convertible Debt
Debt Instrument, Redemption [Line Items]
Conversion Rate, adjusted	10.0722
Approximate Conversion Price, adjusted	$ 99.28
Incremental Share Factor, adjusted	5.0361
Maximum Conversion Rate, adjusted	14.3529
2015 Senior Subordinated Convertible Debt
Debt Instrument, Redemption [Line Items]
Conversion Rate, adjusted	15.7069
Approximate Conversion Price, adjusted	$ 63.67
Incremental Share Factor, adjusted	7.8534
Maximum Conversion Rate, adjusted	21.9896
2017 Junior Subordinated Convertible Debt
Debt Instrument, Redemption [Line Items]
Conversion Rate, adjusted	10.2521
Approximate Conversion Price, adjusted	$ 97.54
Incremental Share Factor, adjusted	5.1261
Maximum Conversion Rate, adjusted	14.3529

Debt and Credit Facility Amorti

Debt and Credit Facility Amortization and Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Amortization of debt issuance costs			$ 4,952	$ 3,182
Amortization of debt discount on convertible debt			$ 79,017	36,907
2017 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Remaining period, in years, over which unamortized debt discount will be recognized as non-cash interest expense (in years)			9 years 1 month 16 days
2015 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Remaining period, in years, over which unamortized debt discount will be recognized as non-cash interest expense (in years)			7 years 1 month 16 days
2017 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Remaining period, in years, over which unamortized debt discount will be recognized as non-cash interest expense (in years)			19 years 1 month 16 days
Convertible Debt
Debt Instrument [Line Items]
Amortization of debt issuance costs	$ 900	$ 500	$ 2,700	1,300
Amortization of debt discount on convertible debt	26,700	12,500	79,000	36,900
Coupon interest expense	19,300	10,100	58,100	30,300
Total	$ 46,900	$ 23,100	$ 139,800	$ 68,500

Debt and Credit Facility (Detai

Debt and Credit Facility (Details) - USD ($) $ in Thousands, shares in Millions	1 Months Ended				3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Nov. 30, 2017	Jun. 30, 2017	Feb. 28, 2017	Feb. 28, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017	Mar. 31, 2015
Debt Instrument [Line Items]
Loss on settlement of convertible debt					$ 2,140	$ 0		$ 15,966	$ 0	$ 43,900	$ 50,600
Amount of unamortized debt discount of debentures					1,399,800		$ 1,399,800	1,399,800		1,516,500
Debt issuance costs			$ 33,700		41,900		41,900	41,900		46,800
Equity portion of convertible debt issuance costs			12,500
Induced conversion of convertible debt expense			5,000
2017 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Proceeds from issuance of senior subordinated convertible debentures, net of issuance costs			2,043,600
Amount of unamortized debt discount of debentures					629,300		629,300	629,300		667,500
Debt issuance costs					16,500		16,500	16,500		17,600
Debt portion of convertible debt issuance costs			17,800
2015 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Proceeds from issuance of senior subordinated convertible debentures, net of issuance costs				$ 1,694,700
Amount of unamortized debt discount of debentures					412,100		412,100	412,100		446,600
Debt issuance costs					15,300		15,300	15,300		16,600
Debt portion of convertible debt issuance costs			3,400
Equity portion of convertible debt issuance costs				9,900
2017 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Proceeds from issuance of senior subordinated convertible debentures, net of issuance costs			567,700
Amount of unamortized debt discount of debentures					358,400		358,400	358,400		309,300
Debt issuance costs				30,300	3,400		3,400	3,400		3,400
Debt portion of convertible debt issuance costs				20,400
2007 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Loss on settlement of convertible debt		$ 13,800					2,100
Amount of unamortized debt discount of debentures					0		0	0		93,100
Debt issuance costs					0		0	0		$ 700
Long-term Debt | 2017 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Proceeds from issuance of senior subordinated convertible debentures, net of issuance costs		111,300
Stock issued during period, value, conversion of convertible securities		119,300
Amount of unamortized debt discount of debentures					$ 55,100		55,100	55,100
Long-term Debt | 2007 Junior Subordinated Convertible Debt
Debt Instrument [Line Items]
Extinguishment of debt	$ 14,600	111,300	431,300	575,000			$ 32,400	$ 111,300
Total consideration, extinguishment of debt		374,000	1,293,900	1,134,600
Stock issued during period, value, conversion of convertible securities		$ 254,600	$ 862,700
Stock issued during period, shares, conversion of convertible securities	0.5	3.2	12					3.2
Payment for debt extinguishment or debt prepayment cost	$ 41,000
Total consideration, extinguishment of debt, liability component		$ 56,300	$ 188,000	238,300
Total consideration, extinguishment of debt, equity component		$ 321,100	$ 1,105,900	$ 896,300

Debt and Credit Facility Credit

Debt and Credit Facility Credit Facility (Details)		1 Months Ended	3 Months Ended		9 Months Ended
		Feb. 28, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jun. 30, 2017USD ($)tranche	Mar. 31, 2017USD ($)
Line of Credit Facility [Line Items]
Interest coverage ratio			3.50		3.50
Repayments of lines of credit	[1]				$ 187,000,000	$ 1,078,500,000
Debt issuance costs		$ 33,700,000	$ 41,900,000		$ 41,900,000			$ 46,800,000
Credit Facility								$ 0
Debt instrument, 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%
Interest expense			$ 49,744,000	$ 35,143,000	$ 148,693,000	104,685,000
Revolving credit facility
Line of Credit Facility [Line Items]
Credit agreement maximum borrowing amount							$ 2,774,000,000
Number of commitment tranches | tranche							2
Credit agreement, total leverage ratio, maximum			5		5			5
Credit Agreement, total consolidated debt, maximum			$ 700,000,000		$ 700,000,000
Credit agreement, total leverage ratio, temporary maximum allowed, first four quarters			5.50		5.50
Credit agreement, total leverage ratio, temporary maximum allowed, next three quarters			5.25		5.25
Credit agreement, senior leverage ratio, maximum			3.50		3.50
Credit agreement, senior leverage ratio, minimum to obtain additional funding			2.50		2.50
Repayments of lines of credit		1,682,500,000
Debt issuance costs		$ 2,100,000
Credit Facility			$ 0		$ 0
Period for leverage ratio to determine interest rate spread					preceding four fiscal quarters
Interest expense			$ 2,300,000	$ 11,900,000	$ 7,300,000	$ 35,500,000
Interest rate spread on overdue principal in event of default (percentage)			2.00%		2.00%
Interest rate spread on overdue amounts in event of default (percentage)			2.00%		2.00%
Revolving credit facility | 2020 Tranche
Line of Credit Facility [Line Items]
Credit agreement maximum borrowing amount			$ 3,122,300,000		$ 3,122,300,000
Revolving credit facility | Debt instrument interest rate option 2
Line of Credit Facility [Line Items]
Debt instrument, description of variable rate basis					adjusted LIBOR rate (based on one, two, three, or six-month interest periods)
Foreign line of credit
Line of Credit Facility [Line Items]
Credit agreement maximum borrowing amount			125,000,000		$ 125,000,000
Standby letters of credit
Line of Credit Facility [Line Items]
Credit agreement maximum borrowing amount			25,000,000		25,000,000
Line of credit facility swingline loan sublimit
Line of Credit Facility [Line Items]
Credit agreement maximum borrowing amount			$ 25,000,000		$ 25,000,000
Minimum | Revolving credit facility | Debt instrument interest rate option 1
Line of Credit Facility [Line Items]
Spread on variable rate (percentage)					0.25%
Maximum | Revolving credit facility | Debt instrument interest rate option 1
Line of Credit Facility [Line Items]
Spread on variable rate (percentage)					1.25%
Maximum | Revolving credit facility | Debt instrument interest rate option 2
Line of Credit Facility [Line Items]
Spread on variable rate (percentage)					2.25%
[1]	During the nine months ended December 31, 2017, the Company issued $111.3 million principal amount of 2017 Junior Notes and 3.2 million shares of common stock in exchange for $111.3 million principal amount of 2007 Junior Notes. Refer to Note 13 Debt and Credit Facility for further discussion.

Pension Plans (Schedule of Net

Pension Plans (Schedule of Net Pension Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Service costs	$ 390	$ 327	$ 1,131	$ 1,054
Interest costs	253	214	742	698
Amortization of actuarial loss	214	0	630	0
Settlements and curtailments	0	354	(36)	585
Net pension period cost	$ 857	$ 895	$ 2,467	$ 2,337

Pension Plans (Narrative) (Deta

Pension Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Expected periodic pension cost in current fiscal year			$ 3.3
Benefits paid	$ 0.3	$ 0.1	0.6	$ 0.3
Defined benefit plan expected contributions in current fiscal year			$ 0.7
FRANCE | Minimum
Defined Benefit Plan Disclosure [Line Items]
Termination benefits, salary period (in months)			1 month
FRANCE | Maximum
Defined Benefit Plan Disclosure [Line Items]
Termination benefits, salary period (in months)			5 months

Contingencies (Details)

Contingencies (Details) $ in Millions	Dec. 31, 2017USD ($)
Loss Contingencies [Line Items]
Loss contingencies, estimate of possible loss	$ 100
Damages from Product Defects
Loss Contingencies [Line Items]
Loss contingencies, estimate of possible loss	69.7
Indemnification Agreement
Loss Contingencies [Line Items]
Loss contingencies, estimate of possible loss	$ 159

Derivative Instruments Foreign

Derivative Instruments Foreign Currency Exchange Rate Risk (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Percentage of company sales denominated in US dollars			99.00%
Derivative [Line Items]
Gains (losses) on foreign currency derivatives recorded in earnings, net	$ (2.4)	$ 1.3	$ 7.1	$ (0.8)
Foreign Exchange Forward
Derivative [Line Items]
Gains (losses) on foreign currency derivatives recorded in earnings, net	$ (0.3)	$ (3.1)	$ (3.5)	$ (3.1)

Comprehensive (Loss) Income (Sc

Comprehensive (Loss) Income (Schedule of Changes in the Components of AOCI) (Details) $ in Thousands	9 Months Ended
	Dec. 31, 2017USD ($)
Changes in the components of AOCI
Accumulated other comprehensive income (loss) at March 31, 2017	$ 3,270,711
Accumulated other comprehensive loss at December 31, 2017	3,185,075
AOCI Attributable to Parent
Changes in the components of AOCI
Accumulated other comprehensive income (loss) at March 31, 2017	(14,378)
Other comprehensive loss before reclassifications	(8,445)
Amounts reclassified from accumulated other comprehensive loss	630
Net other comprehensive loss	(7,815)
Accumulated other comprehensive loss at December 31, 2017	(22,193)
Unrealized holding gains (losses) on available-for-sale securities
Changes in the components of AOCI
Accumulated other comprehensive income (loss) at March 31, 2017	312
Other comprehensive loss before reclassifications	(6,161)
Amounts reclassified from accumulated other comprehensive loss	0
Net other comprehensive loss	(6,161)
Accumulated other comprehensive loss at December 31, 2017	(5,849)
Minimum pension liability
Changes in the components of AOCI
Accumulated other comprehensive income (loss) at March 31, 2017	(5,263)
Other comprehensive loss before reclassifications	(2,284)
Amounts reclassified from accumulated other comprehensive loss	630
Net other comprehensive loss	(1,654)
Accumulated other comprehensive loss at December 31, 2017	(6,917)
Foreign Currency
Changes in the components of AOCI
Accumulated other comprehensive income (loss) at March 31, 2017	(9,427)
Other comprehensive loss before reclassifications	0
Amounts reclassified from accumulated other comprehensive loss	0
Net other comprehensive loss	0
Accumulated other comprehensive loss at December 31, 2017	$ (9,427)

Comprehensive (Loss) Income (77

Comprehensive (Loss) Income (Schedule of Reclassifications of Recognized Transactions out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (loss)	$ (2,962)	$ 121	$ 7,233	$ (658)
Net income	(251,086)	107,175	108,657	27,731
Unrealized holding gains (losses) on available-for-sale securities | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (loss)	0	(1,433)	0	(1,522)
Net income	(214)	(1,433)	(630)	(1,522)
Amortization of actuarial loss | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (loss)	$ (214)	$ 0	$ (630)	$ 0

Share-Based Compensation (Detai

Share-Based Compensation (Details) - USD ($) $ in Thousands		Apr. 04, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Stock-based compensation expense [Line Items]
Allocated share-based compensation expense			$ 24,003	$ 22,120	$ 70,021	$ 106,089
Income tax benefit			6,604	7,376	21,878	36,622
Net income effect of share-based compensation			17,399	14,744	48,143	69,467
Share-based compensation expense previously capitalized			3,500		10,600
Inventory
Stock-based compensation expense [Line Items]
Income tax benefit			3,100	2,800	8,900	8,300
Share-based compensation expense previously capitalized				3,500		11,300
Cost of Sales
Stock-based compensation expense [Line Items]
Allocated share-based compensation expense			3,494	3,468	10,587	15,465
Research and development
Stock-based compensation expense [Line Items]
Allocated share-based compensation expense			10,921	9,881	31,797	37,569
Selling, General and Administrative
Stock-based compensation expense [Line Items]
Allocated share-based compensation expense			9,588	8,771	27,637	53,055
Atmel Corporation
Stock-based compensation expense [Line Items]
Allocated share-based compensation expense	[1]		3,900		53,300
Share-based compensation expense previously capitalized						4,200
Non cash consideration of certain share-based payment awards		$ 7,500
Accelerated compensation cost					38,800
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09, Excess Tax Benefit Component
Stock-based compensation expense [Line Items]
Allocated share-based compensation expense			$ 5,700	$ 6,100	$ 19,800	$ 18,600
[1]	During the three and nine months ended December 31, 2017, $3.1 million and $8.9 million, respectively, of share-based compensation expense was capitalized to inventory and $3.5 million and $10.6 million, respectively, of previously capitalized share-based compensation expense in inventory was sold. During the three and nine months ended December 31, 2016, $2.8 million and $8.3 million, respectively, of share-based compensation expense was capitalized to inventory. The amount of share-based compensation included in cost of sales during the three months ended December 31, 2016 included $3.5 million of previously capitalized share-based compensation expense in inventory that was sold. The amount of share-based compensation included in cost of sales during the nine months ended December 31, 2016 included $11.3 million of previously capitalized share-based compensation expense in inventory that was sold and $4.2 million of share-based compensation expense related to the Company's acquisition of Atmel that was not previously capitalized to inventory.

Net (Loss) Income Per Common 79

Net (Loss) Income Per Common Share From Continuing Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net (loss) income from continuing operations	$ (251,086)	$ 107,335	$ 108,657	$ 33,684
Weighted average common shares outstanding	234,106,000	216,210,000	232,278,000	215,360,000
Dilutive effect of stock options and RSUs	0	4,330,000	4,460,000	4,317,000
Anti-dilutive effect of securities	4,400,046
Weighted average common and potential common shares outstanding	234,106,000	235,424,000	248,024,000	233,351,000
Income from continuing operations, per basic share (in USD per share)	$ (1.07)	$ 0.50	$ 0.47	$ 0.16
Income from continuing operations, per diluted share (in USD per share)	$ (1.07)	$ 0.46	$ 0.44	$ 0.14
2007 Junior Subordinated Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of conversion of debt securities, treasury stock method	0	14,883,643	1,734,984	13,673,578
Anti-dilutive effect of securities	398,430
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 23.49	$ 23.93	$ 23.59	$ 24.08
2015 Senior Subordinated Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of conversion of debt securities, treasury stock method	0	0	9,551,342	0
Anti-dilutive effect of securities	11,920,246
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 63.80	$ 65	$ 64.07	$ 65.40
2017 Senior Subordinated Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of conversion of debt securities, treasury stock method	0	0	0	0
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 99.50	$ 0	$ 99.92	$ 0
2017 Junior Subordinated Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of conversion of debt securities, treasury stock method	0	0	0	0
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 97.75	$ 0	$ 98.16	$ 0

Stock Repurchase (Details)

Stock Repurchase (Details) - shares	3 Months Ended	9 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Mar. 31, 2017
Equity [Abstract]
Stock repurchase program, number of shares authorized to be repurchased	15,000,000	15,000,000
Repurchase of common stock (in shares)	0	0
Treasury stock, number of shares held	18,892,165	18,892,165	20,370,075

Dividends (Details)

Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 06, 2018	Feb. 06, 2018	Dec. 05, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dividends, per share (in usd per share)						$ 1.0860
Payments of ordinary dividends						$ 252.4
Dividends declared per common share (in USD per share)			$ 0.3625	$ 0.3625	$ 0.3605	$ 1.0860	$ 1.0800
Dividends, common stock			$ 84.9
Subsequent Event
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dividends declared per common share (in USD per share)		$ 0.3630
Scenario, Forecast
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dividends, common stock	$ 85.2