Subsequent Event (Details) - USD ($)	Nov. 05, 2015	Sep. 30, 2015
Subsequent Event [Line Items]
Percentage of increase in annual base rent, minimum		3.00%
Corporate Headquarters - San Diego, CA \| Subsequent Event
Subsequent Event [Line Items]
Initial term of operating lease	7 years
Base annual rent	$ 125,000
Percentage of increase in annual base rent, minimum	3.00%
Length of renewal term for operating lease	5 years

Lessee Leasing Arrangements, Operating Leases, Base Annual Rent

No definition available.

Name:	lgnd_LesseeLeasingArrangementsOperatingLeasesBaseAnnualRent
Namespace Prefix:	lgnd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Operating leases of lessee contingent rentals basis spread on variable rate, minimum.

+ References

No definition available.

+ Details

Name:	lgnd_OperatingLeasesOfLesseeContingentRentalsBasisSpreadOnVariableRateMinimum
Namespace Prefix:	lgnd_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of the lessee's leasing arrangement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LesseeLeasingArrangementsOperatingLeasesRenewalTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of the lessee's leasing arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=lgnd_CorporateHeadquartersSanDiegoCAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: