Pension and Profit Sharing Plans (Detail) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Pension and Profit Sharing Plans
Annual contributions included in employee benefit expense	$ 451,000	$ 362,000

Amount of cost for employer contribution to multiemployer plan. Multiemployer plan includes, but is not limited to, pension plan determined to be individually significant and insignificant and other postretirement benefit plan.

No definition available.

Name:	glbz_PensionAndOtherPostretirementBenefitExpenseMultiemployerPlanContributionsByEmployer
Namespace Prefix:	glbz_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration