v3.8.0.1

Allowance for Loan Losses - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Allowance of purchase impaired loans	0.95%	1.15%
Additional allowance on credit impaired loans	$ 400,000	$ 200,000
Interest income recognized on impaired loans	$ 0	$ 0

X

- Definition

Additional allowance on credit impaired loans.

+ References

No definition available.

+ Details

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

X

- Definition

Percentage of allowance on purchase impaired loans.

+ References

No definition available.

+ Details

Name:	ffwm_PercentageOfAllowanceOnPurchaseImpairedLoans
Namespace Prefix:	ffwm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of interest income recognized on a cash-basis method of accounting that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- References

No definition available.

+ Details

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