Investment and Mortgage-Backed Securities, Available for Sale (Narrative) (Details)	3 Months Ended
Mar. 31, 2021 USD ($)	Jun. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale		$ 586,101,589	$ 572,137,595
Available-for-sale Securities, Fair Value Disclosure		600,587,107	589,324,401
Available For Sale Securities Pledged as Collateral, Amortized Cost Basis		$ 297,000,000.0	$ 263,300,000
Percent of unrealized losses for securities in a continuous loss position for 12 months or more		19.80%	37.00%
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions \| security		76	88
GNMA Mortgage-Backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale		$ 109,500,000	$ 91,700,000
Available-for-sale Securities, Fair Value Disclosure		111,000,000.0	93,400,000
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale		32,300,000	$ 37,000,000.0
Available-for-sale Securities, Fair Value Disclosure		$ 32,700,000
Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Gross Realized Gains	$ 220,239

Available For Sale, Percent of Unrealized Losses for Securities in a Continuous Loss Position, 12 Months or Longer

No definition available.

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- Definition

Available For Sale Securities Pledged as Collateral, Amortized Cost Basis

+ References

No definition available.

+ Details

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

No definition available.

+ Details

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- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

No definition available.

+ Details

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- Definition

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

No definition available.

+ Details

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- Definition

Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27290-111563

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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