v3.26.1
Cover - USD ($)
12 Months Ended
Dec. 31, 2025
Mar. 01, 2026
Jun. 30, 2025
Document Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Transition Report false    
Document Financial Statement Error Correction [Flag] false    
Entity Interactive Data Current Yes    
ICFR Auditor Attestation Flag false    
Amendment Flag false    
Document Period End Date Dec. 31, 2025    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Entity Information [Line Items]      
Entity Registrant Name GRAHAM ALTERNATIVE INVESTMENT FUND II LLC    
Entity Central Index Key 0001461237    
Entity File Number 0-53965    
Entity Tax Identification Number 20-4897149    
Entity Incorporation, State or Country Code DE    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Shell Company false    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
Entity Public Float     $ 36,220,218
Entity Contact Personnel [Line Items]      
Entity Address, Address Line One c/o GRAHAM CAPITAL MANAGEMENT, L.P.    
Entity Address, Address Line Two 40 Highland Avenue    
Entity Address, City or Town Rowayton    
Entity Address, State or Province CT    
Entity Address, Postal Zip Code 06853    
Entity Phone Fax Numbers [Line Items]      
City Area Code 203    
Local Phone Number 899-3400    
Entity Listings [Line Items]      
Entity Common Stock, Shares Outstanding   157,893.71