Note 4 - Loans Held for Investment, Net (Details Textual)	12 Months Ended
Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 3,643,608	$ 5,436,972
Impaired Financing Receivable, Interest Income, Nonaccrual	0	0
Impaired Financing Receivable, Interest Income, Accrual Method, Total	4,000	8,000
Financing Receivable, Modifications, Recorded Investment	$ 54,000	$ 0
Veterans Administration Loan [Member]
Number of Receivable Commitments Outstanding	0	0
Real Estate [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 2,700,000
Nonaccrual Loan Secure Percentage	75.30%
Small Business Administration [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 2,300,000
Nonaccrual Loan Secure Percentage	63.00%
Commercial Real Estate Portfolio Segment [Member]
Loans Receivable, Gross, Commercial, Construction	$ 20,800,000	$ 14,700,000
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 2,993,923	$ 3,483,078

Amount of interest income recognized on loans while in nonaccrual status.

No definition available.

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Namespace Prefix:	bctf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

It represents the percentage of nonaccrual loans secured.

+ References

No definition available.

+ Details

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Namespace Prefix:	bctf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of receivable commitments outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	bctf_
Data Type:	xbrli:integerItemType
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- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

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Period Type:	instant

- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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Period Type:	duration

- Definition

Amount before allowance of commercial construction loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5066-111524

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 210.9-03.7(a)(2))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Details

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