Investment Securities - Schedule of Amortized Cost and Fair Value of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Amortized cost
Due in one year or less	$ 64,611	$ 4,277
Due in one to five years	80,999	161,556
Due in five to ten years	60,133	61,290
Due in over ten years	305,696	234,720
Amortized cost, sub-total	511,439	461,843
Total debt securities	1,613,267	1,705,574
Fair value
Due in one year or less	63,615	4,225
Due in one to five years	74,854	152,181
Due in five to ten years	56,477	57,859
Due in over ten years	265,522	205,084
Fair value, sub-total	460,468	419,349
Total debt securities	1,348,219	1,471,186
Mortgage-backed securities - residential
Amortized cost
Mortgage-backed securities	1,083,311	1,224,522
Total debt securities	1,083,311	1,224,522
Fair value
Mortgage-backed securities	871,074	1,034,193
Total debt securities	871,074	1,034,193
Mortgage-backed securities - commercial
Amortized cost
Mortgage-backed securities	18,517	19,209
Total debt securities	18,517	19,209
Fair value
Mortgage-backed securities	16,677	17,644
Total debt securities	$ 16,677	$ 17,644