Business Combination, Common Stock Conversion, Common Share Exchange Ratio

No definition available.

Name:	asrt_BusinessCombinationCommonStockConversionCommonShareExchangeRatio
Namespace Prefix:	asrt_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Business Combination, Pro Forma Information, Earnings Or Loss Of Acquiree, Excluded

+ References

No definition available.

+ Details

Name:	asrt_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeExcluded
Namespace Prefix:	asrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Class Of Warrant Or Right, Exercise Cap, Aggregate Ownership Percentage

+ References

No definition available.

+ Details

Name:	asrt_ClassOfWarrantOrRightExerciseCapAggregateOwnershipPercentage
Namespace Prefix:	asrt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Issued In Connection With Acquisition

+ References

No definition available.

+ Details

Name:	asrt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsIssuedInConnectionWithAcquisition
Namespace Prefix:	asrt_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Issued In Connection With Acquisition, Average Fair Market Value

+ References

No definition available.

+ Details

Name:	asrt_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsIssuedInConnectionWithAcquisitionAverageFairMarketValue
Namespace Prefix:	asrt_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Issued In Connection With Acquisition, Value Recognized As Merger Consideration

+ References

No definition available.

+ Details

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

- Definition

Warrant, Exercise Period

+ References

No definition available.

+ Details

Name:	asrt_WarrantExercisePeriod
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

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460

+ Details

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

- Definition

Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e961-128460

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

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

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of vesting of award under share-based payment arrangement.

+ References

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

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

- Details

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

- Details

Name:	srt_CounterpartyNameAxis=asrt_IrokoPharmaceuticalsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_PlanNameAxis=asrt_EquityIncentivePlan2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

ACQUISITIONS - Narrative (Details) $ / shares in Units, shares in Millions		3 Months Ended	4 Months Ended	6 Months Ended	9 Months Ended
	May 20, 2020 USD ($) $ / shares shares	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Sep. 30, 2020 segment	Sep. 30, 2019 USD ($)
Business Acquisition [Line Items]
Number of operating segments \| segment					1
Zyla Life Sciences
Business Acquisition [Line Items]
Merger exchange ratio	2.5
Business transaction costs associated with merger		$ 0		$ 6,600,000
Purchase accounting adjustments, net decrease to goodwill		$ 5,100,000	$ 5,139,000
Issued (in shares) \| shares	5.0
Proforma information adjustment, excluded income from Zyla's January 2019 Reorganization						$ 115,200,000
Zyla Life Sciences \| Iroko \| Warrant Agreements
Business Acquisition [Line Items]
Exercise aggregate ownership percentage maximum threshold	49.00%
Exercise aggregate ownership percentage term	18 months
Zyla Life Sciences \| 2019 Plan
Business Acquisition [Line Items]
Issued (in shares) \| shares	5.0
Issued, average fair market value, per share (in dollars per share) \| $ / shares	$ 0.62
Issued, value recognized as merger consideration	$ 400,000
Zyla Life Sciences \| Stock options, awards and equivalents \| 2019 Plan
Business Acquisition [Line Items]
Merger exchange ratio	2.5
Vesting period	3 years
Zyla Life Sciences \| Stock options, awards and equivalents \| 2019 Plan \| Maximum
Business Acquisition [Line Items]
Term of award (may not exceed)	10 years
Zyla Life Sciences \| Stock options, awards and equivalents \| 2019 Plan \| Minimum
Business Acquisition [Line Items]
Awards vesting by the end of the first year	33.00%