Borrowings and Subordinated Debentures (Details Textual) - USD ($)	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Subordinated debt	$ 867,100,000
Other Borrowings, Fair Value Disclosure	$ 132,030,000	$ 0
Subordinated notes due May 2031
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.52%
Unused lines of Credit
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 0
Line of Credit Facility, Current Borrowing Capacity	180,000,000
Debt Instrument, Unused Borrowing Capacity, Fee	0
American Financial Exchange
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 250,000,000	0
Credit-Link Notes
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	11.00%
Long-term Debt, Percentage Bearing Variable Interest, Amount	$ 132,800,000	0
Net increase (decrease) in borrowings	128,700,000
Secured Debt	2,660,000,000
Other Borrowings, Fair Value Disclosure	132,030,000	0
Federal Home Loan Bank of San Francisco
Debt Instrument [Line Items]
Loans Pledged as Collateral	7,000,000,000
Line of Credit, Current	1,270,000,000	0
Federal Home Loan Bank of San Francisco \| Secured Debt
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	5,800,000,000
Line of Credit, Current	1,270,000,000	0
Federal Home Loan Bank of San Francisco \| Unused lines of Credit
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	112,000,000
Federal Home Loan Bank of San Francisco \| Unsecured Debt
Debt Instrument [Line Items]
Line of Credit, Current	112,000,000	0
Federal Reserve Bank Advances [Member]
Debt Instrument [Line Items]
Loans Pledged as Collateral	3,100,000,000
Line of Credit Facility, Amount Outstanding	0	$ 0
Federal Reserve Bank Advances [Member] \| Secured Debt
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	$ 2,500,000,000

Other Borrowings, Fair Value Disclosure

No definition available.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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No definition available.

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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.

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No definition available.

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- Definition

Amount of commitment fees for the unused borrowing capacity under the long-term financing arrangement that is available to the entity.

+ References

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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The carrying value as of the balance sheet date of the current portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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- Definition

Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

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- Definition

The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

+ References

No definition available.

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The net cash inflow or outflow in aggregate debt due to repayments and proceeds from additional borrowings.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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