Segment and Related Information - Reconciliation of Financial Data from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Assets	$ 1,392,876		$ 1,392,876			$ 1,321,537
Liabilities	1,259,577		1,259,577			1,170,440
Stockholders' equity	133,299	$ 148,098	133,299	$ 148,098	$ 152,392	151,097	$ 145,507	$ 137,625
Interest and dividend income	11,656	13,098	35,712	38,063
Interest expense	1,240	2,002	4,442	5,828
Net interest and dividend income	10,416	11,096	31,270	32,235
Provision for Loan Losses	1,200	175	4,000	550
Net interest and dividend income after provision for loan losses	9,216	10,921	27,270	31,685
Noninterest income	2,173	1,966	6,693	6,245
Noninterest expense	28,968	8,257	47,042	25,934
(Loss) income before income tax (benefit) expense	(17,579)	4,630	(13,079)	11,996
Income tax (benefit) expense	(184)	884	640	2,346
NET (LOSS) INCOME	(17,395)	3,746	(13,719)	9,650
Operating Segments | CB Financial Services, Inc.
Segment Reporting Information [Line Items]
Undistributed net income (loss) of subsidiary	(18,694)		(15,991)
Operating Segments | Community Bank
Segment Reporting Information [Line Items]
Assets	1,392,537		1,392,537			1,321,001
Liabilities	1,264,864		1,264,864			1,178,759
Stockholders' equity	127,673		127,673			142,242
Interest and dividend income	11,639	13,083	35,664	38,018
Interest expense	1,240	2,002	4,442	5,828
Net interest and dividend income	10,399	11,081	31,222	32,190
Provision for Loan Losses	1,200	175	4,000	550
Net interest and dividend income after provision for loan losses	9,199	10,906	27,222	31,640
Noninterest income	1,208	1,018	3,760	2,966
Noninterest expense	28,046	7,401	44,227	23,209
Undistributed net income (loss) of subsidiary	73	90	433	340
(Loss) income before income tax (benefit) expense	(17,566)	4,613	(12,812)	11,737
Income tax (benefit) expense	(166)	846	590	2,171
NET (LOSS) INCOME	(17,400)	3,767	(13,402)	9,566
Operating Segments | Insurance Brokerage Services Segment | Exchange Underwriters, Inc.
Segment Reporting Information [Line Items]
Assets	4,408		4,408			4,076
Liabilities	1,701		1,701			1,194
Stockholders' equity	2,707		2,707			2,882
Interest and dividend income	1	1	3	2
Interest expense	0	0	0	0
Net interest and dividend income	1	1	3	2
Provision for Loan Losses	0	0	0	0
Net interest and dividend income after provision for loan losses	1	1	3	2
Noninterest income	1,024	984	3,426	3,212
Noninterest expense	919	853	2,806	2,716
(Loss) income before income tax (benefit) expense	106	132	623	498
Income tax (benefit) expense	33	42	190	158
NET (LOSS) INCOME	73	90	433	340
Operating Segments | Insurance Brokerage Services Segment | CB Financial Services, Inc.
Segment Reporting Information [Line Items]
Assets	133,314		133,314			151,124
Liabilities	15		15			27
Stockholders' equity	133,299		133,299			151,097
Interest and dividend income	1,310	1,318	2,634	3,955
Interest expense	0	0	0	0
Net interest and dividend income	1,310	1,318	2,634	3,955
Provision for Loan Losses	0	0	0	0
Net interest and dividend income after provision for loan losses	1,310	1,318	2,634	3,955
Noninterest income	(59)	(36)	(493)	67
Noninterest expense	3	3	9	9
Undistributed net income (loss) of subsidiary		2,463		5,654
(Loss) income before income tax (benefit) expense	(17,446)	3,742	(13,859)	9,667
Income tax (benefit) expense	(51)	(4)	(140)	17
NET (LOSS) INCOME	(17,395)	3,746	(13,719)	9,650
Net Eliminations
Segment Reporting Information [Line Items]
Assets	(137,383)		(137,383)			(154,664)
Liabilities	(7,003)		(7,003)			(9,540)
Stockholders' equity	(130,380)		(130,380)			$ (145,124)
Interest and dividend income	(1,294)	(1,304)	(2,589)	(3,912)
Interest expense	0	0	0	0
Net interest and dividend income	(1,294)	(1,304)	(2,589)	(3,912)
Provision for Loan Losses	0	0	0	0
Net interest and dividend income after provision for loan losses	(1,294)	(1,304)	(2,589)	(3,912)
Noninterest income	0	0	0	0
Noninterest expense	0	0	0	0
Undistributed net income (loss) of subsidiary	18,621	(2,553)	15,558	(5,994)
(Loss) income before income tax (benefit) expense	17,327	(3,857)	12,969	(9,906)
Income tax (benefit) expense	0	0	0	0
NET (LOSS) INCOME	$ 17,327	$ (3,857)	$ 12,969	$ (9,906)