Statements of Capital Accounts (Parenthetical)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Annualized Dividend Rate on Capital Stock	7.00%	8.51%	7.50%

Amount of dividends paid and recorded during the period, including dividends on mandatorily redeemable capital stock, annualized rate. The FHLBank of San Francisco’s (Bank) Board of Directors amended the Bank’s Excess Stock Repurchase, Retained Earnings, and Dividend Framework and was approved to include the Bank’s new dividend philosophy to endeavor to pay a quarterly dividend at an annualized rate between 5% and 7%, which was intended to be considered by the Bank’s Board of Directors beginning with the Bank’s second quarter 2017 dividend declaration. The decision to declare any dividend and the dividend rate are at the discretion of the Bank’s Board of Directors, which may choose to follow the dividend philosophy as guidance in the dividend declaration.

No definition available.

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