Note 9 - Deposits (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Time Deposits, $250,000 or More	$ 148,900	$ 87,300
Interest-bearing and Noninterest-bearing Deposit, Brokered	1,700	0
Certificates of Deposit Issued Through CDARS	$ 17,300	$ 13,700

Amount of interest-bearing and noninterest-bearing third-party deposits placed by or through the assistance of a deposit broker, also known as brokered deposit liabilities.

No definition available.

Name:	cofs_InterestBearingAndNoninterestBearingDepositBrokered
Namespace Prefix:	cofs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant