Long-Term Debt (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jan. 31, 2014	Sep. 21, 2012
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Trust preferred securities issued	$ 113,406	$ 113,406	$ 175,000	$ 111,000
Texas Capital Bancshares Statutory Trust I
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Date issued	Nov. 19, 2002
Trust preferred securities issued	$ 10,310
Floating or fixed rate securities	Floating
Maturity date	Nov. 30, 2032
Texas Capital Bancshares Statutory Trust I | LIBOR
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Interest rate on subordinated debentures	3 month LIBOR + 3.35%
Interest rate on subordinated debentures, spread on variable rate	3.35%
Texas Capital Statutory Trust II
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Date issued	Apr. 10, 2003
Trust preferred securities issued	$ 10,310
Floating or fixed rate securities	Floating
Maturity date	Apr. 30, 2033
Texas Capital Statutory Trust II | LIBOR
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Interest rate on subordinated debentures	3 month LIBOR + 3.25%
Interest rate on subordinated debentures, spread on variable rate	3.25%
Texas Capital Statutory Trust III
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Date issued	Oct. 06, 2005
Trust preferred securities issued	$ 25,774
Floating or fixed rate securities	Floating
Maturity date	Dec. 31, 2035
Texas Capital Statutory Trust III | LIBOR
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Interest rate on subordinated debentures	3 month LIBOR + 1.51%
Interest rate on subordinated debentures, spread on variable rate	1.51%
Texas Capital Statutory Trust IV
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Date issued	Apr. 28, 2006
Trust preferred securities issued	$ 25,774
Floating or fixed rate securities	Floating
Maturity date	Jun. 30, 2036
Texas Capital Statutory Trust IV | LIBOR
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Interest rate on subordinated debentures	3 month LIBOR + 1.60%
Interest rate on subordinated debentures, spread on variable rate	1.60%
Texas Capital Statutory Trust V
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Date issued	Sep. 29, 2006
Trust preferred securities issued	$ 41,238
Floating or fixed rate securities	Floating
Maturity date	Dec. 31, 2036
Texas Capital Statutory Trust V | LIBOR
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Interest rate on subordinated debentures	3 month LIBOR + 1.71%
Interest rate on subordinated debentures, spread on variable rate	1.71%