Borrowings and Subordinated Debentures - Narrative (Details) - USD ($)	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Other Borrowings, Fair Value Disclosure	$ 123,782,000			$ 132,030,000
Proceeds from (Repayments of) Debt	4,533,706,000	$ 1,864,815,000
Assets Sold under Agreements to Repurchase, Carrying Amount	$ 1,260,743,000			$ 0
Assets Sold under Agreements to Repurchase, Interest Rate	8.50%			0.00%
Reserve Account Required Percent	1.50%
Debt Issuance Costs, Gross	$ 4,500,000		$ 17,900,000
Issued Debt Accrued Exit Fees			$ 400,000
Assets Sold Under Agreements To Repurchase Collateralized Amount, Principal Balance	$ 2,000,000,000
One to Nine Months
Debt Instrument [Line Items]
Assets Sold under Agreements to Repurchase, Interest Rate	8.50%
Ten to 18 months
Debt Instrument [Line Items]
Assets Sold under Agreements to Repurchase, Interest Rate	8.75%
Unused Lines of Credit
Debt Instrument [Line Items]
Amount outstanding	$ 0			$ 0
Current borrowing capacity	100,000,000
Unused commitment fees	0
AFX short-term borrowings
Debt Instrument [Line Items]
Current outstanding				250,000,000
Amount outstanding	0			250,000,000
Credit-Link Notes
Debt Instrument [Line Items]
Other Borrowings, Fair Value Disclosure	123,782,000			$ 132,030,000
Secured Debt	$ 2,510,000,000
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	16.00%			14.56%
Credit-Link Notes | Initial Rate Spread
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	10.68%
Credit-Link Notes | Highest Rate of Spread
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	13.25%
Credit-Link Notes | Lowest Rate of Spread
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	8.00%
Repurchase Agreements
Debt Instrument [Line Items]
Securities Loaned, Fair Value of Collateral	$ 2,100,000,000
Secured Debt, Repurchase Agreements	$ 1,400,000,000
Debt Instrument, Term	1 year 6 months
Federal Reserve Bank Advances
Debt Instrument [Line Items]
Amount outstanding	$ 0			$ 0
Federal Reserve Bank Advances | Secured Debt [Member]
Debt Instrument [Line Items]
Borrowing capacity description	6,500,000,000
Securities Loaned, Fair Value of Collateral	1,500,000,000
Collateralized Financings	6,800,000,000
Federal Reserve Bank Advances | Secured Debt [Member] | Bank Term Funding Program
Debt Instrument [Line Items]
Borrowing capacity description	4,900,000,000
Securities Loaned, Fair Value of Collateral	4,900,000,000
Federal Home Loan Bank of San Francisco
Debt Instrument [Line Items]
Securities Loaned, Fair Value of Collateral	18,400,000
Collateralized Financings	8,500,000,000
Federal Home Loan Bank of San Francisco | Secured Debt [Member]
Debt Instrument [Line Items]
Borrowing capacity description	4,300,000,000
Current outstanding	0			1,270,000,000
Federal Home Loan Bank of San Francisco | FHLB unsecured overnight advance
Debt Instrument [Line Items]
Current outstanding	$ 0			$ 112,000,000