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Securities, HTM Debt Securities, Contractual Maturities (Details) $ in Thousands	Mar. 31, 2021 USD ($) Issuer	Dec. 31, 2020 USD ($) Issuer
Held-to-maturity Securities, Debt Maturities, Amortized Cost [Abstract]
Within one year	$ 18,116
From one to five years	57,331
From five to ten years	228,313
After ten years	289,239
Amortized cost	592,999	$ 616,560
Held-to-maturity Securities, Debt Maturities, Estimated Fair Value [Abstract]
Within one year	18,155
From one to five years	58,621
From five to ten years	227,625
After ten years	295,775
Fair value	$ 600,176	$ 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

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