Note 9 - Subsequent Event (Details Textual) - Subsequent Event [Member]	Oct. 26, 2017 shares
Stock Repurchase Program, Number of Shares Authorized to be Repurchased, Percentage	5.00%
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	171,910

The percentage of the number of shares authorized compared to the total shares outstanding, to be repurchased by an entity's Board of Directors under a stock repurchase plan.

No definition available.

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