Investment Securities - Income Earned on Securities (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Non-taxable:
Total	$ 21,573	$ 18,943
Held-to-maturity
Taxable:
Taxable	513	171
Non-taxable:
Non-taxable	2,004	72
Available-for-sale
Taxable:
Taxable	9,607	12,581
Non-taxable:
Non-taxable	$ 9,449	$ 6,119

Interest income, securities, operating, by non-0taxable status [abstract]

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Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities exempt from state, federal and other income tax.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.2)
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Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities subject to state, federal and other income tax.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(b))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
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