Available-For-Sale Securities - Summarizes Available for Sale Securities (Detail) $ in Thousands	Jun. 30, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	$ 80,957
Available-for-sale Securities, Gross Unrealized Gains	32
Available-for-sale Securities, Gross Unrealized Losses	(42)
Available-for-sale Securities, Fair Value	80,947
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	59,421
Available-for-sale Securities, Gross Unrealized Gains	22
Available-for-sale Securities, Gross Unrealized Losses	(11)
Available-for-sale Securities, Fair Value	59,432
Short-term Investments [Member] \| Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	3,965
Available-for-sale Securities, Fair Value	3,965
Short-term Investments [Member] \| Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	10,000
Available-for-sale Securities, Fair Value	10,000
Short-term Investments [Member] \| Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	43,455
Available-for-sale Securities, Gross Unrealized Gains	21
Available-for-sale Securities, Gross Unrealized Losses	(11)
Available-for-sale Securities, Fair Value	43,465
Short-term Investments [Member] \| U.S. Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	2,001
Available-for-sale Securities, Gross Unrealized Gains	1
Available-for-sale Securities, Fair Value	2,002
Long Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	21,536
Available-for-sale Securities, Gross Unrealized Gains	10
Available-for-sale Securities, Gross Unrealized Losses	(31)
Available-for-sale Securities, Fair Value	21,515
Long Term Investments [Member] \| Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	21,536
Available-for-sale Securities, Gross Unrealized Gains	10
Available-for-sale Securities, Gross Unrealized Losses	(31)
Available-for-sale Securities, Fair Value	$ 21,515

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

+ References

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of debt securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 2
-Subparagraph (b)-(g)
-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CashAndCashEquivalentsAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtSecurityAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtSecurityAxis=us-gaap_USGovernmentDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=mdvn_LongTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: