Fair Value Disclosures (Narrative) (Details) (USD $) In Millions	Jun. 30, 2011
Fair Value Disclosures
Impaired loan carrying amount	$ 18.6
Impaired loans valuation allowance	3.2
Impaired loans fair value net	$ 15.4

Name:

ffin_ImpairedLoansValuationAllowanceFairValueDisclosure

Namespace Prefix:

ffin

Data Type:

xbrli:monetaryItemType

Balance Type:

debit

Period Type:

instant