Loans Receivable and Allowance for Credit Losses - Composition of Loans Held-for-Investment- Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Accrued interest receivable	$ 165.5	$ 107.4
Asset Pledged as Collateral
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans receivable pledged to secure borrowings and provide additional borrowing capacity from the FRB and FHLB	$ 25,010.0	$ 27,670.0

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.

No definition available.

+ Details

Name:	us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969

+ Details

Name:	us-gaap_FinancialInstrumentsOwnedAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, before allowance for credit loss, of accrued interest on financing receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 3B
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL120267963-210447

+ Details

Name:	us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_PledgedStatusAxis=us-gaap_AssetPledgedAsCollateralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: