Segment and Related Information - Segment Performance Based on Income (Loss) before Interest Income and Other Income and Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenue	$ 184,393us-gaap_Revenues	$ 204,060us-gaap_Revenues	$ 353,230us-gaap_Revenues	$ 406,527us-gaap_Revenues
Depreciation and amortization	6,036us-gaap_DepreciationAndAmortization	2,438us-gaap_DepreciationAndAmortization	11,990us-gaap_DepreciationAndAmortization	4,811us-gaap_DepreciationAndAmortization
Segment operating income (loss)	36,342us-gaap_OperatingIncomeLoss	82,999us-gaap_OperatingIncomeLoss	62,262us-gaap_OperatingIncomeLoss	165,903us-gaap_OperatingIncomeLoss
Molecular Diagnostics
Segment Reporting Information [Line Items]
Revenue	179,149	196,158	343,656	389,144
Depreciation and amortization	4,991	1,467	9,969	2,830
Segment operating income (loss)	59,017	98,233	104,101	195,981
Pharmaceutical and Clinical Services
Segment Reporting Information [Line Items]
Revenue	5,244	7,902	9,574	17,383
Depreciation and amortization	450	489	899	989
Segment operating income (loss)	(1,011)	1,052	(2,794)	2,889
Research
Segment Reporting Information [Line Items]
Depreciation and amortization	595	482	1,122	992
Segment operating income (loss)	$ (21,664)	$ (16,286)	$ (39,045)	$ (32,967)

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

Name:	us-gaap_DepreciationAndAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

Name:	us-gaap_OperatingIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mygn_MolecularDiagnosticsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mygn_PharmaceuticalAndClinicalServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_ResearchMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: