Note 4 - Financial Instruments With Off-balance-sheet Risk (Details Textual)	Sep. 30, 2017	Dec. 31, 2016
Financial Standby Letter of Credit [Member]
Number of Conditional Commitments Outstanding	1	0

The number of conditional commitments outstanding.

No definition available.

Name:	bctf_NumberOfConditionalCommitmentsOutstanding
Namespace Prefix:	bctf_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant