v3.26.3
SIGNIFICANT ACCOUNTING POLICIES - Fees, Expenses, and Realized Gains (Losses) (Details) - USD ($)
3 Months Ended 7 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2025
Sep. 30, 2026
Dec. 31, 2025
SIGNIFICANT ACCOUNTING POLICIES [Abstract]          
Sponsor's fee rate       0.19%  
Threshold value of fund's assets on basis of which Sponsor's fee is determined       $ 10,000,000,000  
Sponsor's fees $ 7,243 $ 2,750 $ 5,053 17,192  
Extraordinary or non-routine expenses 0 0 0 $ 0  
Number of business days to transfer ownership of Bitcoin       1 day  
Provision for income taxes       $ 0 $ 0
Unrecognized tax benefits 0     $ 0 0
Franklin Crypto Index ETF [Member]          
SIGNIFICANT ACCOUNTING POLICIES [Abstract]          
Sponsor's fee rate       0.19%  
Threshold value of fund's assets on basis of which Sponsor's fee is determined       $ 10,000,000,000  
Sponsor's fees 7,243 2,750 5,053 17,192  
Extraordinary or non-routine expenses 0 $ 0 $ 0 $ 0  
Number of business days to transfer ownership of Bitcoin       1 day  
Provision for income taxes       $ 0 0
Unrecognized tax benefits $ 0     0 $ 0
Maximum [Member]          
SIGNIFICANT ACCOUNTING POLICIES [Abstract]          
Ordinary legal fees and expenses assumed by the sponsor       500,000  
Maximum [Member] | Franklin Crypto Index ETF [Member]          
SIGNIFICANT ACCOUNTING POLICIES [Abstract]          
Ordinary legal fees and expenses assumed by the sponsor       $ 500,000