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Investment Securities - Additional Information (Details) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2021 USD ($) Security | Dec. 31, 2020 USD ($) Security
Schedule Of Available For Sale Securities [Line Items] |  |
Equity securities, at fair value | $ 348,000 | $ 218,000
Tax rate used to calculate tax-equivalent yields (in hundredths) | 21.00% |
Percentage investment book value exceeds stockholders' equity (in hundredths) | 10.00% |
Debt securities, available-for-sale, restricted | $ 740,000,000 | $ 531,000,000
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Number of securities in unrealized loss positions | Security | 1 | 1
12 months or longer, fair value | $ 9,649,000 | $ 9,649,000
12 months or longer, unrealized losses | $ 351,000 | $ 351,000
Held-to-maturity, securities in unrealized loss positions, qualitative disclosure, number of positions | Security | 0 | 0
Obligations of States and Political Subdivisions |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Number of securities in unrealized loss positions | Security | 0 | 0
Mortgage-backed Securities: GSE Residential |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Number of securities in unrealized loss positions | Security | 11 | 2
12 months or longer, fair value | $ 93,000 | $ 2,377,000
12 months or longer, unrealized losses | $ 1,000 | $ 0
Other Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Number of securities in unrealized loss positions | Security | 0 | 0

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- Definition Amount of restricted investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 954 -SubTopic 210 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120413173&loc=SL6242262-115580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 954 -SubTopic 210 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120413209&loc=SL6242269-115581 + Details
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