ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration of Risk (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) manufacturer item	Dec. 31, 2017 USD ($)
Concentration Risk [Line Items]
Accounts receivable related to product sales	$ 23,100	$ 71,900
Accounts receivable, net	37,211	72,482
Accounts receivable balances related to royalties	0	500
Receivables from Collegium
Concentration Risk [Line Items]
Accounts receivable, net		$ 0
License Agreement \| Slan
Concentration Risk [Line Items]
Receivables from collaborative partner	4,600
Collegium Pharmaceutical Inc \| Commercialization Agreement
Concentration Risk [Line Items]
Prepaid expense and other assets	2,800
Collegium Pharmaceutical Inc \| Commercialization Agreement \| Receivables from Collegium
Concentration Risk [Line Items]
Accounts receivable, net	$ 14,011
Customer concentration risk \| Consolidated revenue
Concentration Risk [Line Items]
Number of major distributors \| item	3
Supplier concentration risk \| Gralise
Concentration Risk [Line Items]
Number of third-party contract manufacturers for the supply of gabapentin \| manufacturer	1
Number of third-party suppliers for the supply of gabapentin \| item	1

Accounts Receivable Related To Product Sales

No definition available.

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Balance Type:	debit
Period Type:	instant

- Definition

Represents the amount of accounts receivable related to royalties.

+ References

No definition available.

+ Details

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- Definition

Concentration Risk, Number Of Third-Party Contract Manufacturers

+ References

No definition available.

+ Details

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- Definition

Represents the number of distributors of the entity.

+ References

No definition available.

+ Details

Name:	asrt_NumberOfDistributors
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Balance Type:	na
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- Definition

Represents the number of third-party suppliers for the supply of gabapentin, the active pharmaceutical ingredient.

+ References

No definition available.

+ Details

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- Definition

Represents the amount of receivables from collaborative partners of the entity.

+ References

No definition available.

+ Details

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- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Reference 2: 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(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	debit
Period Type:	instant

- 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

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- Definition

Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets.

+ References

No definition available.

+ Details

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

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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