Investment Securities - Income Earned on Securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest Income, Securities, Operating, by Taxable Status [Abstract]
Total	$ 64,533	$ 63,376	$ 53,460
Held-to-maturity
Interest Income, Securities, Operating, by Taxable Status [Abstract]
Taxable	985	1,207	2,157
Non-taxable	919	1,412	7,424
Available-for-sale
Interest Income, Securities, Operating, by Taxable Status [Abstract]
Taxable	34,054	42,412	37,068
Non-taxable	$ 28,575	$ 18,345	$ 6,811

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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
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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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
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