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Investment Securities - Additional Information (Details) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2020 USD ($) Security | Dec. 31, 2019 USD ($) Security
Schedule Of Available For Sale Securities [Line Items] |  |
Equity securities, at fair value | $ 185,000 | $ 412,000
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 | $ 563,000,000 | $ 688,000,000
U.S. Treasury Securities and Obligations of U.S. Government Corporations & Agencies |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Held-to-maturity, securities in unrealized loss positions, qualitative disclosure, number of positions | Security | 0 | 4
Debt securities, held-to-maturity, continuous unrealized loss position, 12 months or longer, fair value |  | $ 24,565,000
Debt securities, held-to-maturity, continuous unrealized loss position, 12 months or longer, accumulated loss |  | 44,000
Obligations of States and Political Subdivisions |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Debt securities, held-to-maturity, continuous unrealized loss position, 12 months or longer, fair value |  | 347,000
Debt securities, held-to-maturity, continuous unrealized loss position, 12 months or longer, accumulated loss |  | $ 1,000
Number of securities in unrealized loss positions | Security | 0 | 1
Mortgage-backed Securities: GSE Residential |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Number of securities in unrealized loss positions | Security | 2 | 14
12 months or longer, fair value | $ 4,991,000 | $ 20,888,000
12 months or longer, unrealized losses | $ 0 | $ 190,000
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 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729 + Details
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