Long-Term Debt - Schedule Of Long-term Debt Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Borrowed Funds
Junior subordinated debentures	$ 72,166	$ 72,166
CoBiz Statutory Trust I | 3-month LIBOR
Borrowed Funds
Interest rate terms, spread over reference rate	2.95%
CoBiz Capital Trust II | 3-month LIBOR
Borrowed Funds
Interest rate terms, spread over reference rate	2.60%
CoBiz Capital Trust III | 3-month LIBOR
Borrowed Funds
Interest rate terms, spread over reference rate	1.45%
Subordinated notes payable.
Borrowed Funds
Junior subordinated debentures	$ 72,166	72,166
Subordinated notes payable. | CoBiz Statutory Trust I
Borrowed Funds
Junior subordinated debentures	$ 20,619	20,619
Maturity date	Sep. 17, 2033
Earliest call date	Mar. 17, 2017
Subordinated notes payable. | CoBiz Capital Trust II
Borrowed Funds
Junior subordinated debentures	$ 30,928	30,928
Maturity date	Jul. 23, 2034
Earliest call date	Jan. 23, 2017
Subordinated notes payable. | CoBiz Capital Trust III
Borrowed Funds
Junior subordinated debentures	$ 20,619	20,619
Maturity date	Sep. 30, 2035
Earliest call date	Mar. 30, 2017
Subordinated notes payable. | Subordinated notes payable.
Borrowed Funds
Junior subordinated debentures	$ 59,111	$ 59,031
Fixed interest rate	5.625%
Maturity date	Jun. 25, 2030
Earliest call date	Jun. 25, 2025