v3.25.3

DEPOSITS - Additional Information (Details) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2025 | Dec. 31, 2024
DEPOSITS |  |
Large depositor relationships, percentage of total deposits | 2.00% |
Large depositor relationships, consisting of deposit relationships, total deposits | 12.90% | 19.70%
Accrued interest payable on deposits | $ 24.2 | $ 23.3

X
- Definition Represents the large depositor relationships, consisting of deposit relationships exceeded the percentage of total deposits. + References No definition available. + Details
Name: | ffwm_LargeDepositorRelationshipsPercentageExceededOfTotalDeposits
Namespace Prefix: | ffwm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the aggregate percentage of large depositor relationships on total deposits. + References No definition available. + Details
Name: | ffwm_LargeDepositorRelationshipsPercentageOfTotalDeposits
Namespace Prefix: | ffwm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accrued but unpaid interest on deposit liabilities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(15)(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 + Details
Name: | us-gaap_DepositLiabilitiesAccruedInterest
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_DepositsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration