Concentrations of Credit Risk (Details) - Credit concentration risk - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
U.S. Government, its agencies and Government Sponsored Enterprises (GSEs) \| U.S. Government And Government-Sponsored Enterprises
Concentration Risk [Line Items]
Concentration risk amount	$ 1,272.0	$ 1,535.0
Concentration risk percentage	86.00%	87.00%
Non-Government Sponsored Enterprises \| U.S. Government And Government-Sponsored Enterprises
Concentration Risk [Line Items]
Concentration risk amount	$ 167.4	$ 106.1
Non-Government Sponsored Enterprises \| Non-Government Sponsored Enterprises
Concentration Risk [Line Items]
Concentration risk percentage	1.00%	1.00%
Loans Receivable
Concentration Risk [Line Items]
Concentration risk, threshold for major borrower, percentage	3.00%	3.00%
Loans Receivable \| Commercial real estate \| San Francisco
Concentration Risk [Line Items]
Concentration risk percentage	3.00%
Loans on real estate \| Residential loans
Concentration Risk [Line Items]
Concentration risk percentage	90.00%
Loans on real estate \| Commercial real estate \| Commercial real estate, non-owner occupied
Concentration Risk [Line Items]
Concentration risk percentage	6.00%

Concentration Risk, Percentage, Threshold For Major Borrower

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- Definition

Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity.

+ References

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- 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

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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