DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional information (Details) - USD ($) shares in Millions				1 Months Ended	3 Months Ended								12 Months Ended
	Jan. 01, 2019	Aug. 06, 2018	Apr. 30, 2016	Dec. 31, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 02, 2019
Business Combination Purchase Price Before Adjustments		$ 18,000,000
Business Combination, Consideration Transferred		$ 16,700,000
Impairment of Intangible Assets, Finite-lived													$ 75,000	$ 0	$ 903,000
Research and Development Expense													19,806,000	15,388,000	9,070,000
Allocated Share-based Compensation Expense													$ 9,100,000	$ 6,700,000	$ 6,100,000
Short-term Debt, Percentage Bearing Fixed Interest Rate				3.00%	3.00%								3.00%				3.00%
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount													3.0	4.4	4.8
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount															$ 13,400,000
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent													0.40%	26.50%	0.00%
Revenues					$ 47,966,000	$ 51,337,000	$ 54,357,000	$ 52,887,000	$ 57,122,000	$ 50,703,000	$ 47,268,000	$ 46,483,000	$ 206,547,000	$ 201,576,000	$ 176,842,000
Contract with Customer, Asset, Net				$ 100,000	100,000				100,000				100,000	100,000
Deferred Revenue, Current				451,000	451,000				711,000				451,000	711,000	0
Deferred Revenue, Revenue Recognized													10,100,000
Fdic Guaranteed Amount				250,000	250,000								250,000
Payments to Acquire Intangible Assets													20,914,000	$ 5,169,000	$ 97,624,000
Operating Lease, Right-of-Use Asset	$ 500,000
Operating Lease, Liability	$ 500,000			$ 489,000	$ 489,000								$ 489,000
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent us-gaap:OtherLiabilitiesNoncurrent			us-gaap:AccruedLiabilitiesCurrent us-gaap:OtherLiabilitiesNoncurrent	us-gaap:AccruedLiabilitiesCurrent us-gaap:OtherLiabilitiesNoncurrent								us-gaap:AccruedLiabilitiesCurrent us-gaap:OtherLiabilitiesNoncurrent
Prepaid Rent	$ 10,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent													21.00%	21.00%	35.00%
Deferred Tax Assets, Valuation Allowance	100,000			$ 432,000	$ 432,000				2,265,000				$ 432,000	$ 2,265,000
Deferred Tax Liabilities, Net	100,000
Cumulative Effect on Retained Earnings, Net of Tax	$ 2,000
Inventory Reserve Charges				4,600,000	4,600,000
Operating Loss Carryforwards				11,300,000	11,300,000								11,300,000
ANI Canada [Member]
Deferred Tax Assets, Valuation Allowance				400,000	400,000				1,900,000				400,000	1,900,000
Operating Loss Carryforwards				7,900,000	7,900,000				$ 300,000				7,900,000	300,000
Performance Obligation From Prior Period [Member]
Revenues													10,200,000
Sales of contract manufactured products [Member]
Revenue, Remaining Performance Obligation, Amount				8,100,000	8,100,000								8,100,000
Product Development Services [Member]
Revenue, Remaining Performance Obligation, Amount				1,300,000	1,300,000								1,300,000
Drug Applications and Marketing and Distribution Rights [Member] | New Drug Applications [Member]
Impairment of Intangible Assets, Finite-lived													75,000	0	$ 900,000	$ 6,700,000
Employee Stock Purchase Plan 2016 [Member]
Allocated Share-based Compensation Expense													$ 147,000	$ 102,000	$ 68,000
Customer One [Member]
Concentration Risk, Percentage													32.00%	21.00%	29.00%
Customer Two [Member]
Concentration Risk, Percentage													25.00%	23.00%	29.00%
Customer Three [Member]
Concentration Risk, Percentage													23.00%	33.00%	20.00%
Customer One Two And Three [Member]
Concentration Risk, Percentage													88.00%
Two Suppliers 2017 [Member]
Concentration Risk, Percentage															23.00%
One Supplier [Member]
Concentration Risk, Percentage													13.00%	13.00%
Other Sundry Liabilities, Current				$ 700,000	$ 700,000								$ 700,000
Minimum | Product Development Services [Member]
Revenue, Remaining Performance Obligation, Remaining Period				6 months	6 months								6 months
Minimum | Intangible Asset Impairments [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life													4 years
Maximum | Product Development Services [Member]
Revenue, Remaining Performance Obligation, Remaining Period				15 months	15 months								15 months
Maximum | Intangible Asset Impairments [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life													10 years
Cranford Pharmaceuticals [Member] | New Drug Applications [Member]
Payments to Acquire Intangible Assets			$ 60,000,000
Funds Held In Escrow In Relation To Asset Purchase			$ 5,000,000
Building and Building Improvements [Member] | Minimum
Property, Plant and Equipment, Useful Life													20 years
Building and Building Improvements [Member] | Maximum
Property, Plant and Equipment, Useful Life													40 years
Machinery, furniture and equipment [Member] | Minimum
Property, Plant and Equipment, Useful Life													1 year
Machinery, furniture and equipment [Member] | Maximum
Property, Plant and Equipment, Useful Life													10 years