| Cover Page - USD ($) | 12 Months Ended | ||
| Dec. 31, 2019 | Feb. 28, 2020 | Jun. 28, 2019 | |
| Entity Information [Line Items] | |||
| Document Type | 10-K/A | ||
| Document Annual Report | true | ||
| Document Period End Date | Dec. 31, 2019 | ||
| Document Transition Report | false | ||
| Entity File Number | 001-34657 | ||
| Entity Registrant Name | TEXAS CAPITAL BANCSHARES INC/TX | ||
| Entity Incorporation, State or Country Code | DE | ||
| Entity Tax Identification Number | 75-2679109 | ||
| Entity Address, Address Line One | 2000 McKinney Avenue | ||
| Entity Address, Address Line Two | Suite 700 | ||
| Entity Address, City or Town | Dallas | ||
| Entity Address, State or Province | TX | ||
| Entity Address, Country | US | ||
| Entity Address, Postal Zip Code | 75201 | ||
| City Area Code | 214 | ||
| Local Phone Number | 932-6600 | ||
| Entity Well-known Seasoned Issuer | Yes | ||
| Entity Voluntary Filers | No | ||
| Entity Current Reporting Status | Yes | ||
| Entity Interactive Data Current | Yes | ||
| Entity Filer Category | Large Accelerated Filer | ||
| Entity Emerging Growth Company | false | ||
| Entity Small Business | false | ||
| Entity Shell Company | false | ||
| Entity Public Float | $ 3,070,019,000 | ||
| Entity Common Stock, Shares Outstanding | 50,397,277 | ||
| Entity Central Index Key | 0001077428 | ||
| Current Fiscal Year End Date | --12-31 | ||
| Document Fiscal Year Focus | 2019 | ||
| Document Fiscal Period Focus (Q1,Q2,Q3,FY) | FY | ||
| Amendment Flag | true | ||
| Common Stock [Member] | |||
| Entity Information [Line Items] | |||
| Title of 12(b) Security | Common Stock, par value $0.01 per share | ||
| Trading Symbol | TCBI | ||
| Security Exchange Name | NASDAQ | ||
| Series A Preferred Stock [Member] | |||
| Entity Information [Line Items] | |||
| Title of 12(b) Security | 6.5% Non-Cumulative Perpetual Preferred Stock Series A, par value $0.01 per share | ||
| Trading Symbol | TCBIP | ||
| Security Exchange Name | NASDAQ |
