Fair Value Measurements (Details) (USD $) In Thousands	12 Months Ended
Mar. 31, 2011	Mar. 31, 2010
Assets [Abstract]
Fair value measured on recurring basis, money market fund deposits	$ 464,669	$ 206,376
Fair value measured on recurring basis, deposit accounts	239,254	285,754
Fair value measured on recurring basis, government agency bonds	430,591	389,394
Fair value measured on recurring basis, municipal bonds	11,457	157,705
Fair value measured on recurring basis, auction rate securities	12,475	37,237
Fair value measured on recurring basis corporate bonds and debt	523,026	394,856
Fair value measured on recurring basis, marketable equity	26,861	58,402
Fair value measured on recurring basis, total assets	1,708,333	1,531,538
Fair value measured on recurring basis, cash and cash equivalents	703,923	492,130
Fair value measured on recurring basis, short-term investments	539,572	722,193
Fair value measured on recurring basis, long-term investments	464,838	317,215
Fair value measured on recurring basis, total assets	1,708,333	1,531,538
Total gains or losses (realized and unrealized): [Abstract]
Fair value, measurement with unobservable inputs reconciliation, ending	264,778	37,237
Level 1 [Member]
Assets [Abstract]
Fair value measured on recurring basis, money market fund deposits	464,669	206,376
Fair value measured on recurring basis, deposit accounts	0	0
Fair value measured on recurring basis, government agency bonds	0	0
Fair value measured on recurring basis, municipal bonds	0	0
Fair value measured on recurring basis, auction rate securities	0	0
Fair value measured on recurring basis corporate bonds and debt	0	0
Fair value measured on recurring basis, marketable equity	26,861	58,402
Fair value measured on recurring basis, total assets	491,530	264,778
Fair value measured on recurring basis, cash and cash equivalents	464,669	206,376
Fair value measured on recurring basis, short-term investments	16,553	58,402
Fair value measured on recurring basis, long-term investments	10,308
Fair value measured on recurring basis, total assets	491,530	264,778
Level 2 [Member]
Assets [Abstract]
Fair value measured on recurring basis, money market fund deposits	0	0
Fair value measured on recurring basis, deposit accounts	239,254	285,754
Fair value measured on recurring basis, government agency bonds	430,591	389,394
Fair value measured on recurring basis, municipal bonds	11,457	157,705
Fair value measured on recurring basis, auction rate securities	0	0
Fair value measured on recurring basis corporate bonds and debt	519,526	394,856
Fair value measured on recurring basis, marketable equity	0	0
Fair value measured on recurring basis, total assets	1,200,828	1,227,709
Fair value measured on recurring basis, cash and cash equivalents	239,254	285,754
Fair value measured on recurring basis, short-term investments	523,019	638,891
Fair value measured on recurring basis, long-term investments	438,555	303,064
Fair value measured on recurring basis, total assets	1,200,828	1,227,709
Level 3 [Member]
Assets [Abstract]
Fair value measured on recurring basis, money market fund deposits	0	0
Fair value measured on recurring basis, deposit accounts	0	0
Fair value measured on recurring basis, government agency bonds	0	0
Fair value measured on recurring basis, municipal bonds		0
Fair value measured on recurring basis, auction rate securities	12,475	37,237
Fair value measured on recurring basis corporate bonds and debt	3,500	0
Fair value measured on recurring basis, marketable equity	0	0
Fair value measured on recurring basis, total assets	15,975	39,051
Fair value measured on recurring basis, short-term investments		24,900
Fair value measured on recurring basis, long-term investments	15,975	14,151
Fair value measured on recurring basis, total assets	15,975	39,051
Auction rate securities [Member]
Total gains or losses (realized and unrealized): [Abstract]
Fair value, measurement with unobservable inputs reconciliation, beginning	37,237	46,800
Included in earnings	138	(2,538)
Included in other comprehensive income (loss)	0	0
Purchases, sales, issuances, and settlements, net	(24,900)	(7,025)
Transfer into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, measurement with unobservable inputs reconciliation, ending		37,237
Put Option on Auction Rate Securities [Member]
Total gains or losses (realized and unrealized): [Abstract]
Fair value, measurement with unobservable inputs reconciliation, beginning	1,814	4,026
Included in earnings	(1,814)	(2,212)
Included in other comprehensive income (loss)	0	0
Purchases, sales, issuances, and settlements, net	0	0
Transfer into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, measurement with unobservable inputs reconciliation, ending		1,814
Corporate Debt [Member]
Total gains or losses (realized and unrealized): [Abstract]
Fair value, measurement with unobservable inputs reconciliation, beginning	0	0
Included in earnings	0	0
Included in other comprehensive income (loss)	0	0
Purchases, sales, issuances, and settlements, net	3,500	0
Transfer into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, measurement with unobservable inputs reconciliation, ending		0
Total Gains (Losses) [Member]
Total gains or losses (realized and unrealized): [Abstract]
Fair value, measurement with unobservable inputs reconciliation, beginning	0	0
Included in earnings	(1,676)	(4,750)
Included in other comprehensive income (loss)	0	0
Purchases, sales, issuances, and settlements, net	0	0
Transfer into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, measurement with unobservable inputs reconciliation, ending		$ 0

This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset (i.e. auction rate securities), measured at fair value on a recurring basis.

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- Definition

This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset (i.e. corporate bonds and debt), measured at fair value on a recurring basis.

+ Details

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- Definition

This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset (i.e. deposit accounts), measured at fair value on a recurring basis.

+ Details

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Namespace Prefix:	mchp
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- Definition

This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset (i.e. government agency bonds), measured at fair value on a recurring basis.

+ Details

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- Definition

This element represents a certain statement of financial position asset caption which represents a class of assets (i.e. long-term investments), or which may include an individual asset, measured at fair value on a recurring basis.

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- Definition

This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset (i.e. marketable equity), measured at fair value on a recurring basis.

+ Details

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- Definition

This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset (i.e. money market fund deposits), measured at fair value on a recurring basis.

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- Definition

This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset (i.e. municipal bonds), measured at fair value on a recurring basis.

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- Definition

This element represents a certain statement of financial position asset caption which represents a class of assets (i.e. short-term investments), or which may include an individual asset, measured at fair value on a recurring basis.

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- Definition

This element represents total assets measured at fair value on a recurring basis.

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- Definition

This element represents transfers in to assets measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period.

+ Details

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Balance Type:	debit
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- Definition

This element represents transfers out of assets measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period.

+ Details

Name:	mchp_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOut
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Data Type:	xbrli:stringItemType
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- Definition

This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset, measured at fair value on a recurring basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph a

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- Definition

This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or resulted in a change in net asset value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph c(1)

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- Definition

This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in other comprehensive income (a separate component of shareholders' equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph c(1)

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- Definition

This element represents purchases, sales, issuances, and settlements (net) which have taken place during the period in relation to assets measured at fair value on a recurring basis using unobservable inputs (Level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph c(2)

+ Details

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- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph c

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