Regulatory Matters - Additional Information (Details)	3 Months Ended	9 Months Ended
Mar. 31, 2020	Sep. 30, 2020
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer rate	2.50%	2.50%
ASU 2016-13
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Regulatory capital calculation CECL transition adjustment		25.00%
Regulatory capital calculation CECL transition relief period		2 years
Percentage of fixed transition adjustment phased out of regulatory capital calculations over three year		75.00%
Percentage of fixed transition adjustment phased out of regulatory capital calculations in year four		50.00%
Percentage of fixed transition adjustment phased out of regulatory capital calculations in year five		25.00%

Capital conservation buffer rate.

No definition available.

Name:	tbk_CapitalConservationBufferRate
Namespace Prefix:	tbk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of quarterly increase in allowance for credit losses subsequent to adoption of ASU 2016-13 which will not impact capital ratio calculations for a 2 year period.

+ References

No definition available.

+ Details

Name:	tbk_RegulatoryCapitalCalculationCECLTransitionAdjustment
Namespace Prefix:	tbk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Length of time for which the impact of ASU 2016-13 on capital ratio calculations will be delayed.

+ References

No definition available.

+ Details

Name:	tbk_RegulatoryCapitalCalculationCECLTransitionReliefPeriod
Namespace Prefix:	tbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cumulative transition relief adjustments remaining in regulatory capital calculation in year five.

+ References

No definition available.

+ Details

Name:	tbk_RegulatoryCapitalCalculationCECLTransitionReliefPhaseOutPercentRecognizedYearFive
Namespace Prefix:	tbk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cumulative transition relief adjustments remaining in regulatory capital calculation in year four.

+ References

No definition available.

+ Details

Name:	tbk_RegulatoryCapitalCalculationCECLTransitionReliefPhaseOutPercentRecognizedYearFour
Namespace Prefix:	tbk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cumulative transition relief adjustments remaining in regulatory capital calculation in year three.

+ References

No definition available.

+ Details

Name:	tbk_RegulatoryCapitalCalculationCECLTransitionReliefPhaseOutPercentRecognizedYearThree
Namespace Prefix:	tbk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201613Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: