Convertible Line of Credit – Related Party and Supplemental Convertible Lines of Credit – Related Party - Schedule of Credit Facility Terms (Details) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2026 USD ($) $ / shares shares
Original Line of Credit [Member]
Convertible Line of Credit – Related Party and Supplemental Convertible Lines of Credit – Related Party [Abstract]
Agreement Date	Jul. 25, 2022
Commitment \| $	$ 60.0
Draw Period	Jul. 31, 2024
Current Maturity (after Dec. 2025 extension)	Jun. 30, 2027
Conversion Floor Price (in Dollars per share) \| $ / shares	$ 3.00
Warrants Authorized (in Shares) \| shares	1,700,000
Warrant Expiration	Jul. 31, 2029
Supplemental LOC (2024) [Member]
Convertible Line of Credit – Related Party and Supplemental Convertible Lines of Credit – Related Party [Abstract]
Agreement Date	Mar. 29, 2024
Commitment \| $	$ 10.0
Draw Period	Mar. 31, 2025
Current Maturity (after Dec. 2025 extension)	Jun. 30, 2027
Conversion Floor Price (in Dollars per share) \| $ / shares	$ 3.00
Warrants Authorized (in Shares) \| shares	200,000
Warrant Expiration	Jul. 31, 2029
November 2024 Supplemental LOC [Member]
Convertible Line of Credit – Related Party and Supplemental Convertible Lines of Credit – Related Party [Abstract]
Agreement Date	Nov. 14, 2024
Commitment \| $	$ 6.0
Draw Period	May 31, 2025
Current Maturity (after Dec. 2025 extension)	Jun. 30, 2027
Conversion Floor Price (in Dollars per share) \| $ / shares	$ 3.00
Warrants Authorized (in Shares) \| shares	120,000
Warrant Expiration	Jul. 31, 2029
March 2025 Supplemental LOC [Member]
Convertible Line of Credit – Related Party and Supplemental Convertible Lines of Credit – Related Party [Abstract]
Agreement Date	Mar. 31, 2025
Commitment \| $	$ 5.0
Draw Period	Sep. 30, 2025
Current Maturity (after Dec. 2025 extension)	Jun. 30, 2027
Conversion Floor Price (in Dollars per share) \| $ / shares	$ 3.00
Warrants Authorized (in Shares) \| shares	100,000
Warrant Expiration	Jul. 31, 2029
July 2025 Supplemental LOC [Member]
Convertible Line of Credit – Related Party and Supplemental Convertible Lines of Credit – Related Party [Abstract]
Agreement Date	Jul. 08, 2025
Commitment \| $	$ 10.0
Draw Period	Apr. 30, 2026
Current Maturity (after Dec. 2025 extension)	Jun. 30, 2027
Conversion Floor Price (in Dollars per share) \| $ / shares	$ 3.00
Warrants Authorized (in Shares) \| shares	200,000
December 2025 Supplemental LOC [Member]
Convertible Line of Credit – Related Party and Supplemental Convertible Lines of Credit – Related Party [Abstract]
Agreement Date	Dec. 19, 2025
Commitment \| $	$ 10.0
Draw Period	Jan. 31, 2027
Current Maturity (after Dec. 2025 extension)	Jun. 30, 2027
Conversion Floor Price (in Dollars per share) \| $ / shares	$ 4.38
Warrants Authorized (in Shares) \| shares	200,000

Date the credit facility drawdown period, in YYYY-MM-DD format.

No definition available.

Name:	galt_LineOfCreditFacilityDrawDownPeriod
Namespace Prefix:	galt_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-3

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

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-SubTopic 20
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-Paragraph 5
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Date the credit facility terminates, in YYYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480657/210-10-S50-8

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility first became available, in YYYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInitiationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477657/942-210-S45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13)(3)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
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-Section 50
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-Subparagraph (b)
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-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Expiration date of outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur, in YYYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=galt_SupplementalLOC2024Member
Namespace Prefix:
Data Type:	na
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- Details

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Data Type:	na
Balance Type:
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- Details

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Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
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Period Type:

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