Certain Transfers of Financial Assets Certain Transfers of Financial Assets (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Outstanding balance:
Beginning balance	$ 2,568,362	$ 1,949,785
Loans purchased and originated	2,356,710	1,550,059
Payments and loans sold	(4,165,492)	(1,617,518)
Ending balance	759,580	1,882,326
Fair value adjustment:
Fair value over (under) outstanding balance	8,772	19,689
Increase/(decrease) to fair value	5,712	(378)
Fair value over (under) outstanding balance	14,484	19,311
Loans held for sale	774,064	1,901,637	$ 2,577,134
Small Business Administration Loans [Member]
Fair value adjustment:
Fair value over (under) outstanding balance	$ 5,800	$ 299

Loans Held-For-Sale, Fair Value Over (Under) Principal Amount Outstanding

No definition available.

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Namespace Prefix:	tcbi_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Loans Receivable Held-For-Sale, Change In Fair Value [Roll Forward]

+ References

No definition available.

+ Details

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- Definition

Loans Receivable Held-for-sale, Increase (Decrease) in Fair Value

+ References

No definition available.

+ Details

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Namespace Prefix:	tcbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The face amount of loans that will be sold to other entities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
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- Definition

Amount, after allowance for bad debt, of additions to loan receivables held-for-sale that are not part of a disposal group.

+ References

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Amount, after allowance for bad debt, of deductions to loan receivables held-for-sale that are not part of a disposal group.

+ References

+ Details

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

- Details

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