Subordinated Debentures and Convertible Notes - Summary of Trust Preferred Securities and Debentures (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 126,000,000.0
Carrying Value of Debentures	102,477,000	$ 101,929,000
Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	126,000,000
Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 102,477,000	$ 102,200,000
Nara Capital Trust III
Subordinated Borrowing [Line Items]
Current Rate	5.56%
Nara Capital Trust III \| Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 5,000,000
Nara Capital Trust III \| Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 5,155,000
Nara Statutory Trust IV
Subordinated Borrowing [Line Items]
Current Rate	5.45%
Nara Statutory Trust IV \| Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 5,000,000
Nara Statutory Trust IV \| Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 5,155,000
Nara Statutory Trust V
Subordinated Borrowing [Line Items]
Current Rate	5.36%
Nara Statutory Trust V \| Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 10,000,000
Nara Statutory Trust V \| Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 10,310,000
Nara Statutory Trust VI
Subordinated Borrowing [Line Items]
Current Rate	4.06%
Nara Statutory Trust VI \| Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 8,000,000
Nara Statutory Trust VI \| Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 8,248,000
Center Capital Trust I
Subordinated Borrowing [Line Items]
Current Rate	5.45%
Center Capital Trust I \| Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 18,000,000
Center Capital Trust I \| Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 14,128,000
Wilshire Trust II
Subordinated Borrowing [Line Items]
Current Rate	4.20%
Wilshire Trust II \| Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 20,000,000
Wilshire Trust II \| Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 15,634,000
Wilshire Trust III
Subordinated Borrowing [Line Items]
Current Rate	3.81%
Wilshire Trust III \| Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 15,000,000
Wilshire Trust III \| Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 11,041,000
Wilshire Trust IV
Subordinated Borrowing [Line Items]
Current Rate	3.79%
Wilshire Trust IV \| Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 25,000,000
Wilshire Trust IV \| Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 17,899,000
Saehan Capital Trust I
Subordinated Borrowing [Line Items]
Current Rate	3.94%
Saehan Capital Trust I \| Trust Preferred Security Amount
Subordinated Borrowing [Line Items]
Trust Preferred Security Amount	$ 20,000,000
Saehan Capital Trust I \| Carrying Value of Debentures
Subordinated Borrowing [Line Items]
Carrying Value of Debentures	$ 14,907,000