Goodwill and Other Intangibles Assets - Intangible assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Carrying Amount	$ 11,833	$ 14,061
Estimated future amortization expense for identifiable intangible assets:
2020	2,100
2021	2,000
2022	1,900
2023	1,800
2024	1,600
Thereafter	2,300
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Amount	25,605
Accumulated Amortization	(13,772)	(11,544)
Carrying Amount	11,833	14,061
Amortization expense	$ 2,200	2,500
Center Financial Corporation acquisition | Core deposits
Finite-Lived Intangible Assets [Line Items]
Amortization Period	7 years
Gross Amount	$ 4,100
Accumulated Amortization	(4,100)	(4,100)
Carrying Amount	$ 0	0
Pacific International Bancorp, Inc. acquisition | Core deposits
Finite-Lived Intangible Assets [Line Items]
Amortization Period	7 years
Gross Amount	$ 604
Accumulated Amortization	(602)	(579)
Carrying Amount	$ 2	25
Foster Bankshares Inc acquisition | Core deposits
Finite-Lived Intangible Assets [Line Items]
Amortization Period	10 years
Gross Amount	$ 2,763
Accumulated Amortization	(2,120)	(1,893)
Carrying Amount	$ 643	870
Wilshire Bancorp, Inc | Core deposits
Finite-Lived Intangible Assets [Line Items]
Amortization Period	10 years
Gross Amount	$ 18,138
Accumulated Amortization	(6,950)	(4,972)
Carrying Amount	$ 11,188	$ 13,166
Minimum | Core deposits
Finite-Lived Intangible Assets [Line Items]
Amortization Period	7 years
Maximum | Core deposits
Finite-Lived Intangible Assets [Line Items]
Amortization Period	10 years