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Segment and Related Information - Additional Information (Detail) | 12 Months Ended
--- | ---
Jun. 30, 2018 Segment Customer | Jun. 30, 2017 Customer | Jun. 30, 2016 Customer
Segment Reporting [Abstract] |  |  |
Number of reportable segment | Segment | 2 |  |
Number of major customers comprising more than ten10 % of revenues. | Customer | 0 | 0 | 0

X
- Definition Number of major customers comprising more than ten percent of revenues. + References No definition available. + Details
Name: | mygn_NumberOfMajorCustomersComprisingMoreThanTenPercentOfRevenues
Namespace Prefix: | mygn_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References No definition available. + Details
Name: | us-gaap_NumberOfReportableSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_SegmentReportingAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration