FAIR VALUE - Estimated fair values of the Company's financial instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financial assets - Carrying Amount
Cash and due from banks	$ 2,387	$ 2,420
Interest-bearing deposits	31,550	10,017
Federal funds sold	1,042	853
Debt securities	84,534	71,486
Investments in restricted stock	1,199	1,437
Ground rents	140	143
Loans, net	282,571	282,672
Accrued interest receivable	1,226	961
Cash value of life insurance	8,101	8,023
Financial liabilities - Carrying Amount
Deposits	341,937	321,440
Short-term borrowings	37,367	25,000
Accrued interest payable	59	100
Unrecognized financial instruments:
Commitments to extend credit	30,770	26,297
Standby letters of credit	1,044	1,059
Financial assets - Fair Value
Cash and due from banks	2,387	2,420
Interest-bearing deposits	31,550	10,017
Federal funds sold	1,042	853
Investment securities	84,534	71,486
Investments in restricted stock	1,199	1,437
Ground rents	140	143
Loans, less allowance for credit losses	286,728	282,583
Accrued interest receivable	1,226	961
Cash value of life insurance	8,101	8,023
Financial liabilities - Fair Value
Deposits	343,402	300,944
Short-term borrowings	37,383	25,386
Accrued interest payable	59	100
Unrecognized financial instruments:
Commitments to extend credit	30,770	26,297
Standby letters of credit	$ 1,044	$ 1,059

Accrued interest payable fair value

No definition available.

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Period Type:	instant

- Definition

Accrued interest receivable fair value

+ References

No definition available.

+ Details

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Balance Type:	debit
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- Definition

Represents Cash Value of life insurance fair value.

+ References

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Cash and due from banks fair value

+ References

No definition available.

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- Definition

Commitments to extend credit fair value.

+ References

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents commitment to the extend of credit.

+ References

No definition available.

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Namespace Prefix:	glbz_
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Balance Type:	credit
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- Definition

Federal funds sold fair value

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No definition available.

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- References

No definition available.

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- Definition

Ground rents fair value.

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No definition available.

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- Definition

Interest bearing deposit fair value

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No definition available.

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- Definition

Carrying value for banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.

+ References

No definition available.

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Balance Type:	debit
Period Type:	instant

- Definition

This element represents amount of investments in restricted stock.

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No definition available.

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Balance Type:	debit
Period Type:	instant

- Definition

This element represents standby letters of credit.

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No definition available.

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- Definition

Standby letters of credit fair value

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No definition available.

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No definition available.

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- References

No definition available.

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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-Subparagraph (aa)
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Balance Type:	debit
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- Definition

The carrying amount of a life insurance policy on an officer, executive or employee for which the reporting entity (a bank) is entitled to proceeds from the policy upon death of the insured or surrender of the insurance policy.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Period Type:	instant

- Definition

For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(1))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Amount of accrued but unpaid interest on deposit liabilities.

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-SubTopic 210
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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-Paragraph 1
-Subparagraph (SX 210.9-03.12)
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Period Type:	instant

- Definition

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

+ References

No definition available.

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- Definition

The amount outstanding of funds lent to other depository institutions, securities brokers, or securities dealers in the form of Federal Funds sold; for example, immediately available funds lent under agreements or contracts that mature in one business day or roll over under a continuing contract, regardless of the nature of the transaction or the collateral involved, excluding overnight lending for commercial and industrial purposes. Also include Federal Funds sold under agreements to resell on a gross basis, excluding (1) sales of term Federal Funds, (2) due bills representing purchases of securities or other assets by the reporting bank that have not yet been delivered and similar instruments, (3) resale agreements that mature in more than one business day involving assets other than securities, and (4) yield maintenance dollar repurchase agreements.

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-Paragraph 1
-Subparagraph (SX 210.9-03.3)
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- References

No definition available.

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- Definition

Net long-term land leases which are capitalized as part of real property.

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No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

+ References

+ Details

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
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-Subparagraph (SX 210.9-03.7)
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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

No definition available.

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