Note 15 - Shareholders' Equity and Regulatory Matters - (Tables)

12 Months Ended

Dec. 31, 2021

Notes Tables

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block]

											To Be Well
											Capitalized Under
						For Capital					Prompt Corrective
Business First Bancshares, Inc. (Consolidated)	Actual					Adequacy Purposes					Action Provisions
	Amount		Ratio			Amount		Ratio			Amount		Ratio
December 31, 2021:	(Dollars in thousands)
Total Capital (to Risk-Weighted Assets)	$	478,794		11.94	%	$	320,715		8.00	%	$	400,894		10.00	%
Tier 1 Capital (to Risk-Weighted Assets)		367,431		9.17	%		240,537		6.00	%		320,715		8.00	%
Common Equity Tier 1 Capital (to Risk-Weighted Assets)		362,431		9.04	%		180,402		4.50	%		260,581		6.50	%
Tier 1 Leveraged Capital (to Average Assets)		367,431		8.14	%		180,604		4.00	%		225,755		5.00	%
December 31, 2020:
Total Capital (to Risk-Weighted Assets)		N/A		N/A			N/A		N/A			N/A		N/A
Tier 1 Capital (to Risk-Weighted Assets)		N/A		N/A			N/A		N/A			N/A		N/A
Common Equity Tier 1 Capital (to Risk-Weighted Assets)		N/A		N/A			N/A		N/A			N/A		N/A
CBLR	$	340,715		8.79	%	$	310,151		8.00	%		N/A		N/A

											To Be Well
											Capitalized Under
						For Capital					Prompt Corrective
b1BANK	Actual					Adequacy Purposes					Action Provisions
	Amount		Ratio			Amount		Ratio			Amount		Ratio
December 31, 2021:	(Dollars in thousands)
Total Capital (to Risk-Weighted Assets)	$	468,834		11.71	%	$	320,411		8.00	%	$	400,514		10.00	%
Tier 1 Capital (to Risk-Weighted Assets)		438,898		10.96	%		240,308		6.00	%		320,411		8.00	%
Common Equity Tier 1 Capital (to Risk-Weighted Assets)		438,898		10.96	%		180,231		4.50	%		260,334		6.50	%
Tier 1 Leveraged Capital (to Average Assets)		438,898		9.73	%		180,453		4.00	%		225,566		5.00	%
December 31, 2020:
Total Capital (to Risk-Weighted Assets)		N/A		N/A			N/A		N/A			N/A		N/A
Tier 1 Capital (to Risk-Weighted Assets)		N/A		N/A			N/A		N/A			N/A		N/A
Common Equity Tier 1 Capital (to Risk-Weighted Assets)		N/A		N/A			N/A		N/A			N/A		N/A
CBLR	$	358,083		9.24	%	$	310,091		8.00	%		N/A		N/A