Cash flow leverage ratio.

No definition available.

Name:	basi_CashFlowLeverageRatio
Namespace Prefix:	basi_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of debt serve ratio one.

+ References

No definition available.

+ Details

Name:	basi_MinimumDebtServiceCoverageRatioOne
Namespace Prefix:	basi_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: 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(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: 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(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: 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(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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

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

- Definition

Amount of the required periodic payments including both interest and principal payments.

+ References

+ Details

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

- Definition

This item represents the amount that could be realized under a life insurance contract or contracts owned by the Entity as of the date of the statement of financial position. Such Entity-owned life insurance policies are commonly known as corporate-owned life insurance (COLI) or bank-owned life insurance (BOLI).

+ References

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ 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(22))
-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(16))
-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(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of the required periodic payments of both interest and principal.

+ References

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: 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)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: 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(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

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

- Details

Name:	srt_TitleOfIndividualAxis=basi_PresidentAndChiefExecutiveOfficerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=basi_CreditArrangementsMember
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:	us-gaap_LineOfCreditFacilityAxis=basi_FirstInternetBankOfIndianaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=basi_EquipmentDrawLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=basi_ConstructionDrawLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=basi_SmithersAvanzaToxicologyServicesLlcAcquisitionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=basi_PcrsAcquisitionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=basi_InitialTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=basi_SubsequentTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=basi_ThirdTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=basi_FifthTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=basi_FourthTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=basi_CurrentCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=basi_CapexLineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=basi_CapitalExpenditureLineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=basi_SecondCapexLineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

DEBT - Additional Information (Details)		6 Months Ended
DEBT - Additional Information (Details)	Aug. 01, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019 USD ($)
DEBT ARRANGEMENTS
Long-term Debt		$ 20,854,000				$ 15,087,000
Minimum \| President and Chief Executive Officer [Member]
DEBT ARRANGEMENTS
Life Insurance, Corporate or Bank Owned, Amount		$ 5,000,000
Credit Arrangements [Member] \| Maximum
DEBT ARRANGEMENTS
Minimum Debt Service Coverage Ratio One		1.25
Cash Flow Leverage Ratio		5.00	4.00	4.25	4.50
Credit Arrangements [Member] \| Minimum
DEBT ARRANGEMENTS
Minimum Debt Service Coverage Ratio One		1.0
Cash Flow Leverage Ratio		1.00	1.0	1.0	1.00
First Internet Bank of Indiana [Member]
DEBT ARRANGEMENTS
Debt Instrument, Periodic Payment		$ 33,000
Debt Instrument, Interest Rate, Stated Percentage		3.99%
Debt Instrument, Face Amount		$ 4,500,000
Long-term Debt, Gross		3,870,000
First Internet Bank of Indiana [Member] \| Equipment Draw Loan [Member]
DEBT ARRANGEMENTS
Long-term Debt		1,237,000
Line of Credit Facility, Additional Borrowing Capacity		1,429,000
First Internet Bank of Indiana [Member] \| Construction Draw Loan [Member]
DEBT ARRANGEMENTS
Long-term Debt		4,247,000
Line of Credit Facility, Additional Borrowing Capacity		$ 4,445,000
First Internet Bank of Indiana [Member] \| Revolving Credit Facility [Member]
DEBT ARRANGEMENTS
Debt Instrument, Interest Rate, Stated Percentage		4.00%
Line of Credit Facility, Additional Borrowing Capacity		$ 5,000,000
Basis points deducted from prime rate		0.00%
Long-term Line of Credit		$ 2,614,000
Smithers Avanza Toxicology Services LLC acquisition \| Unsecured promissory note
DEBT ARRANGEMENTS
Debt Instrument, Interest Rate, Stated Percentage		6.50%
Debt Instrument, Face Amount		$ 810,000
PCRS acquisition \| Unsecured promissory note
DEBT ARRANGEMENTS
Debt Instrument, Periodic Payment		$ 800,000
Debt Instrument, Interest Rate, Stated Percentage		4.50%
Initial Term Loan [Member]
DEBT ARRANGEMENTS
Long-term Debt		$ 3,870,000				3,990,000
Subsequent Term Loan [Member] \| First Internet Bank of Indiana [Member]
DEBT ARRANGEMENTS
Debt Instrument, Periodic Payment		$ 78,000
Debt Instrument, Interest Rate, Stated Percentage		5.06%
Debt Instrument, Face Amount		$ 5,500,000
Long-term Debt		4,364,000
Third Term Loan
DEBT ARRANGEMENTS
Long-term Debt		1,209,000				1,271,000
Third Term Loan \| First Internet Bank of Indiana [Member]
DEBT ARRANGEMENTS
Debt Instrument, Periodic Payment		$ 20,000
Debt Instrument, Interest Rate, Stated Percentage		4.63%
Debt Instrument, Face Amount		$ 1,271,000
Long-term Debt		1,209,000
Fifth Term loan
DEBT ARRANGEMENTS
Long-term Debt		$ 1,922,000				0
Fifth Term loan \| First Internet Bank of Indiana [Member]
DEBT ARRANGEMENTS
Debt Instrument, Interest Rate, Stated Percentage		4.00%
Debt Instrument, Face Amount		$ 1,939,000
Long-term Debt		1,922,000
Fourth Term Loan
DEBT ARRANGEMENTS
Long-term Debt		$ 1,493,000				$ 0
Fourth Term Loan \| First Internet Bank of Indiana [Member]
DEBT ARRANGEMENTS
Debt Instrument, Interest Rate, Stated Percentage		4.00%
Debt Instrument, Face Amount		$ 1,500,000
Long-term Debt		$ 1,493,000
Current Credit Agreement [Member] \| First Internet Bank of Indiana [Member] \| Equipment Draw Loan [Member]
DEBT ARRANGEMENTS
Debt Instrument, Interest Rate, Stated Percentage		5.20%
Current Credit Agreement [Member] \| First Internet Bank of Indiana [Member] \| Construction Draw Loan [Member]
DEBT ARRANGEMENTS
Debt Instrument, Interest Rate, Stated Percentage		5.20%
Capex Line [Member] \| First Internet Bank of Indiana [Member] \| Capital Expenditure Line of Credit [Member]
DEBT ARRANGEMENTS
Debt Instrument, Face Amount		$ 1,100,000
Long-term Debt		$ 948,000
Basis points deducted from prime rate		4.00%
Line of Credit Facility, Periodic Payment	$ 17,000
Second Capex Line [Member] \| First Internet Bank of Indiana [Member] \| Capital Expenditure Line of Credit [Member]
DEBT ARRANGEMENTS
Debt Instrument, Face Amount		$ 3,000.00
Long-term Debt		$ 1,036,000
Basis points deducted from prime rate		(0.50%)
Second Capex Line [Member] \| First Internet Bank of Indiana [Member] \| Capital Expenditure Line of Credit [Member] \| Base Rate [Member]
DEBT ARRANGEMENTS
Basis points deducted from prime rate		4.00%