Investment Securities - Additional Information (Details)	6 Months Ended
Jun. 30, 2021 USD ($) Security	Dec. 31, 2020 USD ($) Security
Schedule Of Available For Sale Securities [Line Items]
Equity securities, at fair value \| $	$ 301,000	$ 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 \| $	$ 674,000,000	$ 531,000,000
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Schedule Of Available For Sale Securities [Line Items]
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 \| $	$ 121,550,000	$ 2,377,000
12 months or longer, unrealized losses \| $	$ 844,000	$ 0
Other Securities
Schedule Of Available For Sale Securities [Line Items]
Number of securities in unrealized loss positions \| Security	0	0

Percentage investment book value exceeds stockholders' equity.

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

+ References

No definition available.

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- Definition

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer.

+ References

No definition available.

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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
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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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-Publisher FASB
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Disclosure regarding factors used to determine that the impairment of securities categorized as held-to-maturity where cost exceeds fair value is not an other than temporary impairment (OTTI). This item contains disclosure of the number of investment positions in the held-to-maturity investments determined to be temporarily impaired.

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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.

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