Subordinated Debentures - Summary of Trust Preferred Securities and Debentures (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Subordinated Borrowing [Line Items]
Subordinated debentures	$ 101,929	$ 100,853
Nara Capital Trust III
Subordinated Borrowing [Line Items]
Initial Rate	5.94%
Nara Statutory Trust IV
Subordinated Borrowing [Line Items]
Initial Rate	5.29%
Nara Statutory Trust V
Subordinated Borrowing [Line Items]
Initial Rate	5.74%
Nara Statutory Trust VI
Subordinated Borrowing [Line Items]
Initial Rate	4.44%
Center Capital Trust I
Subordinated Borrowing [Line Items]
Initial Rate	5.29%
Wilshire Statutory Trust II [Member]
Subordinated Borrowing [Line Items]
Initial Rate	4.58%
Wilshire Statutory Trust III [Member]
Subordinated Borrowing [Line Items]
Initial Rate	4.19%
Wilshire Statutory Trust IV [Member]
Subordinated Borrowing [Line Items]
Initial Rate	4.17%
Saehan Capital Trust I [Member]
Subordinated Borrowing [Line Items]
Initial Rate	4.42%
Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 126,000
Trust Preferred Security Amount \| Nara Capital Trust III
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	5,000
Trust Preferred Security Amount \| Nara Statutory Trust IV
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	5,000
Trust Preferred Security Amount \| Nara Statutory Trust V
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	10,000
Trust Preferred Security Amount \| Nara Statutory Trust VI
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	8,000
Trust Preferred Security Amount \| Center Capital Trust I
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	18,000
Trust Preferred Security Amount \| Wilshire Statutory Trust II [Member]
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	20,000
Trust Preferred Security Amount \| Wilshire Statutory Trust III [Member]
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	15,000
Trust Preferred Security Amount \| Wilshire Statutory Trust IV [Member]
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	25,000
Trust Preferred Security Amount \| Saehan Capital Trust I [Member]
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	20,000
Subordinated Debentures Amount
Subordinated Borrowing [Line Items]
Subordinated debentures	101,929
Subordinated Debentures Amount \| Nara Capital Trust III
Subordinated Borrowing [Line Items]
Subordinated debentures	5,155
Subordinated Debentures Amount \| Nara Statutory Trust IV
Subordinated Borrowing [Line Items]
Subordinated debentures	5,155
Subordinated Debentures Amount \| Nara Statutory Trust V
Subordinated Borrowing [Line Items]
Subordinated debentures	10,310
Subordinated Debentures Amount \| Nara Statutory Trust VI
Subordinated Borrowing [Line Items]
Subordinated debentures	8,248
Subordinated Debentures Amount \| Center Capital Trust I
Subordinated Borrowing [Line Items]
Subordinated debentures	14,026
Subordinated Debentures Amount \| Wilshire Statutory Trust II [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures	15,526
Subordinated Debentures Amount \| Wilshire Statutory Trust III [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures	10,948
Subordinated Debentures Amount \| Wilshire Statutory Trust IV [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures	17,758
Subordinated Debentures Amount \| Saehan Capital Trust I [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures	$ 14,803