Investment Securities - Qualified Affordable Housing Projects (Details) - Affordable Housing Investment Fund $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2021 USD ($) investment	Dec. 31, 2020 USD ($) investment
Summary of Investment Holdings [Line Items]
Affordable housing project investments	$ 4.0	$ 4.0
Number of investments \| investment	5	5
Income (loss) on affordable housing investment funds	$ 1.5	$ 1.2

Number Of Investments

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- Definition

Amount of investment in qualified affordable housing projects.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 740
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116633289&loc=SL49122993-202985

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- Definition

Amount of investment income (loss) of qualified affordable housing project investments accounted for using the equity method.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 740
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=116633289&loc=SL49122993-202985

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- Definition

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+ References

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