Investments - AFS, Debt Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost		$ 1,292,500
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated fair value, available-for-sale securities	$ 0	1,292,500
Due in one year or less
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost		246,500
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated fair value, available-for-sale securities		246,500
Due after one year and through five years
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost		1,046,000
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated fair value, available-for-sale securities		1,046,000
Due after five years and through ten years
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost		0
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated fair value, available-for-sale securities		0
Due after ten years
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost		0
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated fair value, available-for-sale securities		0
Total
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost		1,292,500
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated fair value, available-for-sale securities		$ 1,292,500

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	mchp_ScheduleOfAvailableForSaleSecuritiesDebtMaturitiesAxis=mchp_DueInOneYearOrLessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mchp_ScheduleOfAvailableForSaleSecuritiesDebtMaturitiesAxis=mchp_DueAfterOneYearAndThroughFiveYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mchp_ScheduleOfAvailableForSaleSecuritiesDebtMaturitiesAxis=mchp_DueAfterFiveYearsAndThroughTenYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mchp_ScheduleOfAvailableForSaleSecuritiesDebtMaturitiesAxis=mchp_DueAfterTenYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mchp_ScheduleOfAvailableForSaleSecuritiesDebtMaturitiesAxis=mchp_TotalMaturitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: