XML 68 R56.htm IDEA: XBRL DOCUMENT v3.24.3

FAIR VALUE - Narrative (Details) - investment	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Number of investments transferred	1	8	1

X

- Definition

Number of Investments Transferred

+ References

No definition available.

+ Details

Name:	chmg_NumberOfInvestmentsTransferred
Namespace Prefix:	chmg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	us-gaap_FairValueDisclosuresAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration