Commitments and Contingencies - Off Balance Sheet Arrangements of Bank (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies
Commitments to fund new loans	$ 36,143	$ 54,687
Commitments to fund under existing loans, lines of credit	517,169	473,646
Commitments under standby letters of credit	$ 15,589	$ 10,769

Commitments to fund under existing loans lines of credit.

No definition available.

Name:	ffwm_CommitmentsToFundUnderExistingLoansLinesOfCredit
Namespace Prefix:	ffwm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant