Investment Securities - Schedule of Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Amortized cost
Due in one year or less	$ 19,614	$ 21,851
Due in one to five years	121,436	54,847
Due in five to ten years	55,733	45,714
Due in over ten years	252,732	255,077
Amortized cost, sub-total	449,515	377,489
Total debt securities	1,784,458	1,673,798
Fair value
Due in one year or less	19,602	21,884
Due in one to five years	118,438	55,307
Due in five to ten years	54,635	46,975
Due in over ten years	244,287	269,737
Fair value, sub-total	436,962	393,903
Total debt securities	1,683,525	1,678,525
Mortgage-backed securities - residential
Amortized cost
Mortgage-backed securities	1,320,205	1,281,285
Total debt securities	1,320,205	1,281,285
Fair value
Mortgage-backed securities	1,232,256	1,269,372
Total debt securities	1,232,256	1,269,372
Mortgage-backed securities - commercial
Amortized cost
Mortgage-backed securities	14,738	15,024
Total debt securities	14,738	15,024
Fair value
Mortgage-backed securities	14,307	15,250
Total debt securities	$ 14,307	$ 15,250