The period of time the license agreement last following the first commercial sale in the U.S.

No definition available.

Name:	asrt_CollaborativeAgreementTermOfLicenseAgreement
Namespace Prefix:	asrt_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the license fee incurred during the period.

+ References

No definition available.

+ Details

Name:	asrt_LicenseFee
Namespace Prefix:	asrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The period of time the Company is responsible for marketing and selling under the License Agreement.

+ References

No definition available.

+ Details

Name:	asrt_TermForSellingAndMarketing
Namespace Prefix:	asrt_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The period of time the counterparty to the license agreement is responsible for selling, after the Company's term is completed.

+ References

No definition available.

+ Details

Name:	asrt_TermForSellingCounterparty
Namespace Prefix:	asrt_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

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

- Definition

Amount of gain (loss) on sale or disposal of intangible assets.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainLossOnDispositionOfIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=asrt_ArchimedeLazandaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	asrt_AssetAcquisitionAxis=asrt_SlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=asrt_LicenseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

ACQUISITIONS AND DISPOSITIONS - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
	Nov. 07, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Research and development expenses		$ 8,042	$ 13,718	$ 32,631
Gain on divestiture		0	17,064	$ 0
Lazanda
Business Acquisition [Line Items]
Gain on divestiture			$ 17,100
Slan \| License Agreement
Business Acquisition [Line Items]
License agreement term	10 years
Company's marketing and selling term	7 years
Slan's selling term after the Company's	3 years
Research and development expenses	$ 24,900	$ 2,250
License fee	$ 5,000