Contingencies	9 Months Ended
Dec. 31, 2018
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 on April 4, 2016, the Company became involved with the following legal matters: 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"). 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 $227.7 million. The Company's Atmel subsidiaries intend to defend this action vigorously. Individual Labor Actions by former LFR Employees. In June 2010, Atmel Rousset sold its wafer manufacturing business in Rousset, France to LFoundry GmbH ("LF"), the German parent of LFoundry Rousset ("LFR"). LFR then leased the Atmel Rousset facility to conduct the manufacture of wafers. More than three years later, LFR became insolvent and later liquidated. 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 LF was fraudulent and should be voided. Furthermore, new claims have been filed in a regional court in France on behalf of a subset of this same group of employees against Microchip Technology Incorporated and Atmel Corporation. These claims are specious and the defendant entities therefore intend to defend vigorously against these claims. In connection with its acquisition of Microsemi, which closed on May 29, 2018, the Company became involved with the following legal matters: Federal Shareholder Class Action Litigation. Beginning on September 14, 2018, the Company and certain of its officers were named in two putative shareholder class action lawsuits filed in the United States District Court for the District of Arizona, captioned Jackson v. Microchip Technology Inc., et al., Case No. 2:18-cv-02914-JJT and Maknissian v. Microchip Technology Inc., et al., Case No. 2:18-cv-02924-JJT. On November 13, 2018, the Maknissian complaint was voluntarily dismissed. The Jackson complaint is allegedly brought on behalf of a putative class of purchasers of Microchip common stock between March 2, 2018 and August 9, 2018. The complaint asserts claims for alleged violations of the federal securities laws and generally alleges that the defendants issued materially false and misleading statements and failed to disclose material adverse facts about the Company’s business, operations, and prospects during the putative class period. The complaint seeks, among other things, compensatory damages and attorneys’ fees and costs on behalf of the putative class. On December 11, 2018, the Court issued an order appointing the lead plaintiff. An amended complaint is due to be filed on February 8, 2019. Federal Derivative Litigation. On December 17, 2018, a shareholder derivative lawsuit was filed against certain of the Company’s officers and directors in the United States District Court for the District of Arizona, captioned Kistenmacher v. Sanghi, et al., Case No. 16-cv-04720. The Company is named as a nominal defendant. The complaint generally alleges that defendants breached their fiduciary duties by, among other things, making or causing the Company to make false and misleading statements and omissions regarding the Microsemi acquisition, the Company’s business, operations, and prospects, and a purported failure to maintain internal controls. The complaint further alleges that certain defendants engaged in insider trading. The complaint asserts causes of action for alleged violations of Section 14(a) of the Securities Exchange Act, breach of fiduciary duties, and unjust enrichment and seeks unspecified monetary damages, corporate governance reforms, restitution, and attorneys’ fees and costs. State Derivative Litigation. On January 22, 2019, a shareholder derivative lawsuit was filed against certain of the Company’s officers and directors in the Superior Court of Arizona for Maricopa County, captioned Reid v. Sanghi, et al., Case No. CV2019-002389. The Company is named as a nominal defendant. The complaint generally alleges that defendants breached their fiduciary duties by, among other things, purportedly failing to conduct adequate due diligence regarding Microsemi prior to its acquisition, misrepresenting the Company’s business prospects and health, and engaging in improper practices, and further alleges that certain defendants engaged in insider trading. The complaint asserts causes of action for breach of fiduciary duty, waste, and unjust enrichment and seeks unspecified monetary damages, corporate governance reforms, equitable and/or injunctive relief, restitution, and attorneys’ fees and costs. Peterson, et al. v. Sanghi, et al. On October 9, 2018, four former officers of Microsemi Corporation filed a lawsuit in the Superior Court of California in Orange County against us and four of our officers asserting claims for slander per se, libel per se, trade libel, and violations of California Business and Professions Code Section 17200. The complaint seeks unspecified compensatory and punitive damages, injunctive relief, and attorneys’ fees and costs. On November 8, 2018, defendants removed the action to the United States District Court for the Central District of California, Case No. 18-cv-02000-JLS. 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, 2018, 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 $163.7 million. There are some licensing agreements in place that do not specify indemnification limits. As of December 31, 2018, 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.

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 on April 4, 2016, the Company became involved with the following legal matters:

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"). 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 $227.7 million. The Company's Atmel subsidiaries intend to defend this action vigorously.

Individual Labor Actions by former LFR Employees. In June 2010, Atmel Rousset sold its wafer manufacturing business in Rousset, France to LFoundry GmbH ("LF"), the German parent of LFoundry Rousset ("LFR"). LFR then leased the Atmel Rousset facility to conduct the manufacture of wafers. More than three years later, LFR became insolvent and later liquidated. 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 LF was fraudulent and should be voided. Furthermore, new claims have been filed in a regional court in France on behalf of a subset of this same group of employees against Microchip Technology Incorporated and Atmel Corporation. These claims are specious and the defendant entities therefore intend to defend vigorously against these claims.

In connection with its acquisition of Microsemi, which closed on May 29, 2018, the Company became involved with the following legal matters:

Federal Shareholder Class Action Litigation. Beginning on September 14, 2018, the Company and certain of its officers were named in two putative shareholder class action lawsuits filed in the United States District Court for the District of Arizona, captioned Jackson v. Microchip Technology Inc., et al., Case No. 2:18-cv-02914-JJT and Maknissian v. Microchip Technology Inc., et al., Case No. 2:18-cv-02924-JJT. On November 13, 2018, the Maknissian complaint was voluntarily dismissed. The Jackson complaint is allegedly brought on behalf of a putative class of purchasers of Microchip common stock between March 2, 2018 and August 9, 2018. The complaint asserts claims for alleged violations of the federal securities laws and generally alleges that the defendants issued materially false and misleading statements and failed to disclose material adverse facts about the Company’s business, operations, and prospects during the putative class period. The complaint seeks, among other things, compensatory damages and attorneys’ fees and costs on behalf of the putative class. On December 11, 2018, the Court issued an order appointing the lead plaintiff. An amended complaint is due to be filed on February 8, 2019.

Federal Derivative Litigation. On December 17, 2018, a shareholder derivative lawsuit was filed against certain of the Company’s officers and directors in the United States District Court for the District of Arizona, captioned Kistenmacher v. Sanghi, et al., Case No. 16-cv-04720. The Company is named as a nominal defendant. The complaint generally alleges that defendants breached their fiduciary duties by, among other things, making or causing the Company to make false and misleading statements and omissions regarding the Microsemi acquisition, the Company’s business, operations, and prospects, and a purported failure to maintain internal controls. The complaint further alleges that certain defendants engaged in insider trading. The complaint asserts causes of action for alleged violations of Section 14(a) of the Securities Exchange Act, breach of fiduciary duties, and unjust enrichment and seeks unspecified monetary damages, corporate governance reforms, restitution, and attorneys’ fees and costs.

State Derivative Litigation. On January 22, 2019, a shareholder derivative lawsuit was filed against certain of the Company’s officers and directors in the Superior Court of Arizona for Maricopa County, captioned Reid v. Sanghi, et al., Case No. CV2019-002389. The Company is named as a nominal defendant. The complaint generally alleges that defendants breached their fiduciary duties by, among other things, purportedly failing to conduct adequate due diligence regarding Microsemi prior to its acquisition, misrepresenting the Company’s business prospects and health, and engaging in improper practices, and further alleges that certain defendants engaged in insider trading. The complaint asserts causes of action for breach of fiduciary duty, waste, and unjust enrichment and seeks unspecified monetary damages, corporate governance reforms, equitable and/or injunctive relief, restitution, and attorneys’ fees and costs.

Peterson, et al. v. Sanghi, et al. On October 9, 2018, four former officers of Microsemi Corporation filed a lawsuit in the Superior Court of California in Orange County against us and four of our officers asserting claims for slander per se, libel per se, trade libel, and violations of California Business and Professions Code Section 17200. The complaint seeks unspecified compensatory and punitive damages, injunctive relief, and attorneys’ fees and costs. On November 8, 2018, defendants removed the action to the United States District Court for the Central District of California, Case No. 18-cv-02000-JLS.

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, 2018, 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 $163.7 million. There are some licensing agreements in place that do not specify indemnification limits. As of December 31, 2018, 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.