Effective annual interest rate over life of royalty purchase agreement.

No definition available.

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Liability related to sale of future royalties and milestones.

No definition available.

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Non-cash interest expense related to sale of future royalties.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Noncash royalty revenue recognized.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Percentage of purchase of worldwide rights to receive royalties.

No definition available.

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Data Type:	dtr-types:percentItemType
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Period Type:	instant

Proceeds from royalties sold.

No definition available.

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

Prospective effective annual interest rate over life of royalty purchase agreement.

No definition available.

Name:	agen_ProspectiveEffectiveAnnualInterestRateOverLifeOfRoyaltyPurchaseAgreement
Namespace Prefix:	agen_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

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Balance Type:
Period Type:

Name:	us-gaap_ContractWithCustomerDurationAxis=agen_GSKAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_TypeOfArrangementAxis=agen_RoyaltyPurchaseAgreementMember
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Liability Related to the Sale of Future Royalties and Milestones (Narrative) (Details) - USD ($) $ in Thousands		9 Months Ended
	Jan. 19, 2018	Sep. 30, 2021	Jan. 06, 2018
Liability Related To Sale Of Future Royalties And Milestones [Line Items]
Non-cash royalty revenue recognized		$ 28,903
Non-cash interest expense		48,146
HCR [Member] \| GSK Agreements [Member] \| Royalty Purchase Agreement [Member]
Liability Related To Sale Of Future Royalties And Milestones [Line Items]
Percentage of purchase of worldwide rights to receive royalties			100.00%
Gross proceeds received for royalty rights	$ 190,000
Non-cash royalty revenue recognized		28,900
Non-cash interest expense		$ 48,100
Effective annual interest rate		26.90%
Prospective effective annual interest rate		23.10%