Tabular disclosure of the number and weighted-average exercise prices (or conversion ratios) for phantom share options (or share units) that were outstanding at the beginning and end of the year, vested and expected to vest, exercisable or convertible at the end of the year, and the number of share options or share units that were granted, exercised or converted, forfeited, and expired during the year.

No definition available.

Name:	gcbc_ScheduleOfPhantomStockOptionsActivityTableTextBlock
Namespace Prefix:	gcbc_
Data Type:	dtr:textBlockItemType
Balance Type:	na
Period Type:	duration