Equity Incentive Plans, Stock Options Outstanding (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Option shares outstanding beginning balance (in shares)	573,611	2,269,803	3,360,997
Options granted (in shares)	27,654	0	0
Options assumed upon acquisition (in shares)	666,586		827,707
Options exercised (shares)	(477,618)	(1,675,663)	(1,638,548)
Options canceled (in shares)	(105,934)	(20,529)	(280,353)
Option shares outstanding ending balance (in shares)	684,299	573,611	2,269,803
Option shares outstanding beginning balance (in dollars per share)	$ 24.75	$ 25.58	$ 25.00
Options granted (in dollars per shares)	$ 46.66	$ 0.00	$ 0.00
Options assumed upon acquisition (in dollars per share)	$ 29.33		$ 19.32
Options exercised (in dollars per share)	$ 26.42	$ 25.91	$ 22.19
Options canceled (in dollars per share)	$ 28.17	$ 22.78	$ 19.90
Option shares outstanding ending balance (in dollars per share)	$ 28.41	$ 24.75	$ 25.58
Closing price of company's common stock related to calculation of aggregate intrinsic value of stock options (in dollars per share)	$ 48.90mchp_ClosingPriceOfCompanysCommonStock
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Total intrinsic value of options exercised related to stock incentive plans	$ 9.6	$ 25.5	$ 19.0
Aggregate intrinsic value of options outstanding related to stock incentive plans	14.1
Aggregate intrinsic value of options exercisable related to stock incentive plans	$ 6.2
Exercisable number of option shares (in shares)	283,133	543,435
Weighted average exercise price per share of exercisable options (in dollars per share)	$ 26.90	$ 25.03
Weighted average fair value per share of stock options granted	$ 9.00

Closing price per share of company's common stock at balance sheet date

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Net number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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The addition or reduction in the number of reserved shares that could potentially be issued under the option plan attributable to reasons other than grants, exercises, forfeitures, and expirations during the reporting period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted average price at which grantees could acquire or could have acquired the underlying shares with respect to any other type of change in shares reserved for issuance.

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Number of share options (or share units) exercised during the current period.

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