Long-Term Debt - Narrative, Part I (Details) - USD ($) $ in Millions	1 Months Ended			12 Months Ended
	Aug. 31, 2005	May 31, 2004	Sep. 30, 2003	Dec. 31, 2016
CoBiz Statutory Trust I
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Minority interest held in statutory trust			$ 0.6
CoBiz Capital Trust II
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Minority interest held in statutory trust		$ 0.9
CoBiz Capital Trust III
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Minority interest held in statutory trust	$ 0.6
Trust preferred securities | CoBiz Statutory Trust I
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Trust preferred securities, value			20.0
Trust preferred securities, settlement date				Sep. 17, 2033
Proceeds from sale of securities and minority interest			$ 20.6
Trust preferred securities | CoBiz Capital Trust II
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Trust preferred securities, value		30.0
Trust preferred securities, settlement date				Jul. 23, 2034
Proceeds from sale of securities and minority interest		$ 30.9
Trust preferred securities | CoBiz Capital Trust III
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Trust preferred securities, value	20.0
Trust preferred securities, settlement date				Sep. 30, 2035
Proceeds from sale of securities and minority interest	$ 20.6
Minimum | CoBiz Statutory Trust I
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Period of notice required for redemption				30 days
Maximum | CoBiz Statutory Trust I
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Period of notice required for redemption				60 days