Securities, HTM Debt Securities, Contractual Maturities (Details) $ in Thousands	Sep. 30, 2021 USD ($) Issuer	Dec. 31, 2020 USD ($) Issuer
Held-to-maturity Securities, Debt Maturities, Amortized Cost [Abstract]
Within one year	$ 97,203
From one to five years	56,120
From five to ten years	226,478
After ten years	303,302
Amortized cost	683,103	$ 616,560
Held-to-maturity Securities, Debt Maturities, Estimated Fair Value [Abstract]
Within one year	97,239
From one to five years	57,485
From five to ten years	227,026
After ten years	307,379
Fair value	$ 689,129	$ 636,827
Number of issuers whose holdings exceeded 10% of consolidated stockholders' equity, excluding U.S. Government securities and Government-sponsored enterprises securities | Issuer	0	0