Tax cuts and jobs act of 2017, change in tax rate, limitation on deduction of executive compensation.

No definition available.

Name:	mygn_TaxCutsAndJobsActOf2017ChangeInTaxRateLimitationOnDeductionOfExecutiveCompensation
Namespace Prefix:	mygn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Tax cuts and jobs act of 2017 incomplete accounting earnings per share increase.

+ References

No definition available.

+ Details

Name:	mygn_TaxCutsAndJobsActOf2017IncompleteAccountingEarningsPerShareIncrease
Namespace Prefix:	mygn_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of reasonable estimate for income tax expense (benefit) from effect of Tax Cuts and Jobs Act for which accounting for tax effect is incomplete.

+ References

No definition available.

+ Details

Name:	mygn_TaxCutsAndJobsActOf2017IncompleteAccountingProvisionalIncomeTaxExpenseBenefit
Namespace Prefix:	mygn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of reasonable estimate for income tax expense from transition tax on accumulated earnings of controlled foreign corporation deemed repatriated pursuant to Tax Cuts and Jobs Act for which accounting for tax effect is incomplete.

+ References

No definition available.

+ Details

Name:	mygn_TaxCutsAndJobsActOf2017IncompleteAccountingTransitionTaxForAccumulatedForeignEarningsProvisionalIncomeTaxExpense
Namespace Prefix:	mygn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateContinuingOperations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I)
-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Tax year being audited in the income tax examination, in CCYY format.

+ References

No definition available.

+ Details

Name:	us-gaap_IncomeTaxExaminationYearUnderExamination
Namespace Prefix:	us-gaap_
Data Type:	us-types:gYearListItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e38679-109324

+ Details

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

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_ForeignCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TaxPeriodAxis=us-gaap_EarliestTaxYearMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_FederalMinistryOfFinanceGermanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TaxPeriodAxis=us-gaap_LatestTaxYearMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_StateAndLocalJurisdictionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_NewJerseyDivisionOfTaxationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended			6 Months Ended		12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2019	Jun. 30, 2018
Income Tax Contingency [Line Items]
U.S. federal statutory rate	21.00%			21.00%	35.00%		28.00%
Tax Act, incomplete accounting, provisional adjustments		$ (32,600,000)
Earnings per share increase		$ 0.45
Tax Act, limitation on deduction of executive compensation	$ 1,000,000
Tax Act, incomplete accounting, transition tax for accumulated foreign earnings, provisional income tax expense	0
Income tax expense	$ 1,600,000		$ 4,500,000
Approximate rate on pre-tax income	200.00%		5.40%
Scenario, Plan [Member]
Income Tax Contingency [Line Items]
U.S. federal statutory rate						21.00%
Foreign Tax Authority [Member]
Income Tax Contingency [Line Items]
Tax Act, incomplete accounting, provisional adjustments	$ 0
Foreign Tax Authority [Member] \| Earliest Tax Year [Member] \| Federal Ministry of Finance, Germany [Member]
Income Tax Contingency [Line Items]
Tax year being audited in income tax examination	2013
Foreign Tax Authority [Member] \| Latest Tax Year [Member] \| Federal Ministry of Finance, Germany [Member]
Income Tax Contingency [Line Items]
Tax year being audited in income tax examination	2015
State Tax Authority [Member] \| Earliest Tax Year [Member] \| State of New Jersey [Member]
Income Tax Contingency [Line Items]
Tax year being audited in income tax examination	2013
State Tax Authority [Member] \| Latest Tax Year [Member] \| State of New Jersey [Member]
Income Tax Contingency [Line Items]
Tax year being audited in income tax examination	2017