Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands				1 Months Ended
	May 04, 2018	Aug. 20, 2015	Nov. 01, 2014	May 31, 2018	Apr. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Other Intangible Assets
Accumulated amortization						$ 2,382	$ 1,995
United American Bank
Other Intangible Assets
Accumulated amortization						158
Useful life, amortization period	3 years
United American Bank | Core deposit
Other Intangible Assets
Intangible assets acquired				$ 4,771
Useful life, amortization period				10 years
United American Bank | Below market-value lease
Other Intangible Assets
Intangible assets acquired				$ 660
Useful life, amortization period				3 years
Tri Valley Bank
Other Intangible Assets
Accumulated amortization						65
Tri Valley Bank | Core deposit
Other Intangible Assets
Intangible assets acquired					$ 1,768
Useful life, amortization period					10 years
Tri Valley Bank | Below market-value lease
Other Intangible Assets
Intangible assets acquired					$ 210
Useful life, amortization period					11 years
Focus Business Bank | Core deposit
Other Intangible Assets
Intangible assets acquired		$ 6,285
Useful life, amortization period		10 years
BVF/CSNK
Other Intangible Assets
Accumulated amortization						$ 696	$ 601
BVF/CSNK | Below market-value lease
Other Intangible Assets
Intangible assets acquired			$ 109
Useful life, amortization period			3 years
BVF/CSNK | Customer relationship and brokered relationship
Other Intangible Assets
Intangible assets acquired			$ 1,900
Useful life, amortization period			10 years
BVF/CSNK | Non-compete agreement
Other Intangible Assets
Intangible assets acquired			$ 250
Useful life, amortization period			3 years