Parent Only Condensed Financial Information - Schedule of Parent Only Condensed Statements of Financial Condition (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 114,763	$ 147,685
Total assets	2,788,535	2,974,002
Liabilities and Shareholders’ Equity
Reserve for unfunded commitments	826	688
Long term debt	104,049	103,708
Accrued interest and other liabilities	17,359	21,938
Total liabilities	2,380,845	2,599,381
Shareholders' equity:
Common stock	290,395	288,610
Additional paid-in capital	4,938	5,659
Retained earnings	112,046	81,618
Non-controlling interest	72	72
Accumulated other comprehensive income (loss)	239	(1,338)
Total shareholders’ equity	407,690	374,621	$ 265,176	$ 181,585
Total liabilities and shareholders’ equity	2,788,535	2,974,002
RBB Bancorp
Assets
Cash and cash equivalents	29,985	45,540
Other assets	4,202	2,820
Total assets	521,760	488,179
Liabilities and Shareholders’ Equity
Long term debt	104,049	103,708
Subordinated debentures	9,673	9,506
Other liabilities	348	344
Total liabilities	114,070	113,558
Shareholders' equity:
Common stock	290,395	288,610
Additional paid-in capital	4,938	5,659
Retained earnings	112,046	81,618
Non-controlling interest	72	72
Accumulated other comprehensive income (loss)	239	(1,338)
Total shareholders’ equity	407,690	374,621
Total liabilities and shareholders’ equity	521,760	488,179
RBB Bancorp | Royal Business Bank
Assets
Investment	480,703	433,023
RBB Bancorp | Royal Asset Management
Assets
Investment	$ 6,870	$ 6,796