Certain Transfers of Financial Assets Certain Transfers of Financial Assets (Details 4) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Transfers and Servicing [Abstract]
50 bp adverse change in prepayment speed	$ (6,133)	$ (10,768)
100 bp adverse change in prepayment speed	$ (6,954)	$ (17,965)

Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 100 Basis Points Adverse Change in Prepayment Speed

No definition available.

Name:	tcbi_SensitivityAnalysisofFairValueTransferorsInterestsinTransferredFinancialAssetsImpactof100BasisPointsAdverseChangeinPrepaymentSpeed
Namespace Prefix:	tcbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant