Investments with previous credit losses rollforward (Details) $ in Millions	3 Months Ended
Mar. 31, 2025 USD ($)
Investments, Debt and Equity Securities [Abstract]
Total net accretion or amortization recognized in interest income associated with PLRMBS with previous credit losses to the prior methodology	$ 3

This item represents the total accretion or amortization associated with other than temporary impairment (OTTI) of a debt security held or impaired PLRMBS, that was recognized in interest income.

No definition available.

Name:	fhlbsf_OtherthanTemporaryImpairmentCreditLossesRecognizedinEarningsTotalaccretionoramortization
Namespace Prefix:	fhlbsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration