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