v3.8.0.1

Deposits - Additional Information (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
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Deposits [Abstract] |  |
Certificates of deposits of $250,000 or more, maturities within one year | $ 229.7 | $ 182.8
Certificates of deposits of $250,000 or more, maturities after one year | 58.5 | 7.1
Certificates of deposits of $250,000 or more, total | 288.2 | 189.9
Certificates of deposit of less than $ 250,000, maturities within one year | 542.7 | 416.3
Certificates of deposit of less than $ 250,000, maturities after one year | 69.9 | 23.2
Certificates of deposit of less than $250,000, total | $ 612.6 | $ 439.5

X
- Definition Time deposits 250000 or more. + References No definition available. + Details
Name: | ffwm_TimeDeposits250000OrMore
Namespace Prefix: | ffwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Time deposits 250000 or more, maturities after one year. + References No definition available. + Details
Name: | ffwm_TimeDeposits250000OrMoreMaturitiesAfterOneYear
Namespace Prefix: | ffwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Time deposits 250000 or more, maturities with in one year. + References No definition available. + Details
Name: | ffwm_TimeDeposits250000OrMoreMaturitiesWithInOneYear
Namespace Prefix: | ffwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Time deposits less than 250000. + References No definition available. + Details
Name: | ffwm_TimeDepositsLessThan250000
Namespace Prefix: | ffwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Time deposits less than 250000, maturities after one year. + References No definition available. + Details
Name: | ffwm_TimeDepositsLessThan250000MaturitiesAfterOneYear
Namespace Prefix: | ffwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Time deposits less than 250000, maturities with in one year. + References No definition available. + Details
Name: | ffwm_TimeDepositsLessThan250000MaturitiesWithInOneYear
Namespace Prefix: | ffwm_
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