DEPOSITS - Schedule of maturities of time deposits (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Time Deposits, Fiscal Year Maturity [Abstract]
Deposits from public entities	$ 53.3	$ 51.5
Brokered deposits	$ 122.4	$ 104.5

Amount of interest-bearing third-party deposits placed by or through the assistance of a deposit broker, also known as brokered deposit liabilities.

No definition available.

Name:	cbtx_InterestBearingDepositBrokered
Namespace Prefix:	cbtx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant