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Employee Deferred Savings Plan -Company's Recorded Contributions To Plan (Detail) - USD ($) $ in Millions | 12 Months Ended
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Jun. 30, 2015 | Jun. 30, 2014 | Jun. 30, 2013
Savings Plan [Line Items] |  |  |
Deferred savings plan Company contributions | $ 5.1 | $ 4.4 | $ 3.5

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- Definition Savings Plan [Line Items] + References No definition available. + Details
Name: | mygn_SavingsPlanLineItems
Namespace Prefix: | mygn_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition The increase in the fair value of plan assets from contributions made by the employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration