Other Long-Term Liabilities (Other Long-Term Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Other Liabilities [Line Items]
Accrued lease liability	$ 10,700	$ 10,700
Deferred Tax and Other Liabilities, Noncurrent		1,571
Uncertain tax position		37,574
Other Sundry Liabilities		1,020
Total		$ 50,865

[Line Items] for Schedule of Other Liabilities [Table]

No definition available.

Name:	pdli_ScheduleOfOtherLiabilitiesLineItems
Namespace Prefix:	pdli_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and due after one year (or beyond the operating cycle if longer) for contractual rent under lease arrangements.

+ References

+ Details

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

- Definition

Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences, with jurisdictional netting, and liabilities classified as noncurrent and other.

+ References

No definition available.

+ Details

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

- Definition

Amount recognized for uncertainty in income taxes classified as noncurrent.

+ References

+ Details

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

- Definition

Amount of liabilities classified as other, due after one year or the normal operating cycle, if longer.

+ References

+ Details

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

- Definition

The aggregate carrying amount, as of the balance sheets date, of obligations not otherwise itemized or categorized in the footnotes to the financial statements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(24))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(15))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(15))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(20))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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