Carrying value as of the balance sheet date of obligations incurred through that date for payments to licensor.

No definition available.

Name:	mdvn_AccruedPaymentToLicensor
Namespace Prefix:	mdvn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Dollar amount of aggregate milestone payments payable to licensor upon achievement of certain development and regulatory milestone events.

+ References

No definition available.

+ Details

Name:	mdvn_AggregateDevelopmentAndRegulatoryMilestonePaymentsToLicensor
Namespace Prefix:	mdvn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	mdvn_CommitmentsAndContingenciesLineItems
Namespace Prefix:	mdvn_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated life of development and manufacturing services.

+ References

No definition available.

+ Details

Name:	mdvn_EstimatedLifeOfDevelopmentAndManufacturingServices
Namespace Prefix:	mdvn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated of development and manufacturing services amount.

+ References

No definition available.

+ Details

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Namespace Prefix:	mdvn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Dollar amount of future milestone payment for Technology transfer under manufacturing services agreement.

+ References

No definition available.

+ Details

Name:	mdvn_FutureMilestonePaymentForTechnologyTransferUnderManufacturingServicesAgreement
Namespace Prefix:	mdvn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Manufacturing Services and Supply Agreement Period

+ References

No definition available.

+ Details

Name:	mdvn_ManufacturingServicesAndSupplyAgreementPeriod
Namespace Prefix:	mdvn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum dollar amount of milestone payments eligible to be received under a collaboration arrangement.

+ References

No definition available.

+ Details

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Namespace Prefix:	mdvn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum dollar amount of funding for clinical trial materials pursuant to manufacturing services agreement.

+ References

No definition available.

+ Details

Name:	mdvn_MaximumFundingForClinicalTrialMaterials
Namespace Prefix:	mdvn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Dollar amount of milestone payments earned to date pursuant to collaboration agreement.

+ References

No definition available.

+ Details

Name:	mdvn_MilestonePaymentsEarnedToDateUnderCollaborationAgreement
Namespace Prefix:	mdvn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Date which lease or group of leases is set to expire.

+ References

No definition available.

+ Details

Name:	mdvn_OperatingLeaseAgreementsExpirationDate
Namespace Prefix:	mdvn_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Optional lease extension term, in years.

+ References

No definition available.

+ Details

Name:	mdvn_OptionalLeaseExtensionTerm
Namespace Prefix:	mdvn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of all Sublicensing Income, as defined in agreement, payable to licensor.

+ References

No definition available.

+ Details

Name:	mdvn_PercentageOfSublicensingIncome
Namespace Prefix:	mdvn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of royalty on net sales payable to licensor.

+ References

No definition available.

+ Details

Name:	mdvn_RoyaltyPercentagePayableToLicensor
Namespace Prefix:	mdvn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717

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

- Definition

Amount of other research and development expense.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 730

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

+ Details

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

- Details

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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2014 sqft	Dec. 31, 2014 sqft	Dec. 31, 2013	Dec. 31, 2012
Commitments And Contingencies [Line Items]
Operating lease office space, in square feet	142,000us-gaap_AreaOfRealEstateProperty	142,000us-gaap_AreaOfRealEstateProperty
Lease expiry period		December 2019
Rent expense		$ 8,100,000us-gaap_OperatingLeasesRentExpenseNet	$ 5,200,000us-gaap_OperatingLeasesRentExpenseNet	$ 4,600,000us-gaap_OperatingLeasesRentExpenseNet
Business acquisition upfront fee		12,000,000
Total consideration under current statement of work	14,800,000
Estimated of development and manufacturing period	18 months
CureTech Ltd [Member]
Commitments And Contingencies [Line Items]
Milestone payment	5,000,000
CureTech Ltd [Member] \| Pidilizumab [Member]
Commitments And Contingencies [Line Items]
Business acquisition upfront fee	3,000,000
Manufacturing services and supply agreement period	3 years
Milestone payment		5,000,000
Funding for clinical trial materials		19,300,000
Collateralized letters of credit [Member]
Commitments And Contingencies [Line Items]
Outstanding letters of credit collateralized by restricted cash	11,800,000	11,800,000	9,900,000
Current asset [Member] \| Collateralized letters of credit [Member]
Commitments And Contingencies [Line Items]
Outstanding letters of credit collateralized by restricted cash	200,000	200,000
Long-term assets [Member] \| Collateralized letters of credit [Member]
Commitments And Contingencies [Line Items]
Outstanding letters of credit collateralized by restricted cash	11,600,000	11,600,000	9,900,000
Corporate Headquarters [Member]
Commitments And Contingencies [Line Items]
Operating lease office space, in square feet	127,000	127,000
Optional lease extension term		5 years
Development milestone payments [Member]
Commitments And Contingencies [Line Items]
Aggregate milestone payments upon achievement of certain development and regulatory milestone events	2,800,000	2,800,000
Percentage of sublicensing income		10.00%
Royalty percentage on sales		4.00%
Sales milestone payments [Member] \| Astellas Pharma Inc. [Member]
Commitments And Contingencies [Line Items]
Percentage of sublicensing income		10.00%
Milestone payments eligible to earn		320,000,000
Sales milestone payments under collaborative agreement		50,000,000	25,000,000
Accrued payment to sales milestone payments		$ 5,000,000	$ 2,500,000