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.

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.