Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Debt Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Securities available-for-sale
Securities available-for-sale, Less than 1 year, Amortized Cost	$ 11,517	$ 7,443
Securities available-for-sale, 1 to 5 years, Amortized Cost	84,491	31,821
Securities available-for-sale, 5 to 10 years, Amortized Cost	55,856	21,299
Securities available-for-sale, After 10 years, Amortized Cost	74,768	75,592
Securities available-for-sale, before Residential mortgage-backed securities	226,632	136,155
Securities available-for-sale, Residential mortgage-backed securities	842,587	482,156
Securities available-for-sale
Securities available-for-sale, Less than 1 year, Fair Value	11,622	7,532
Securities available-for-sale, 1 to 5 years, Fair Value	85,511	33,227
Securities available-for-sale, 5 to 10 years, Fair Value	56,258	22,021
Securities available-for-sale, After 10 years, Fair Value	78,671	79,897
Securities available-for-sale, before Residential mortgage-backed securities Fair Value	232,062	142,677
Securities available-for-sale, Fair Value	849,315	493,274
Securities held-to-maturity
Securities held-to-maturity, After 10 years, Amortized Cost	10,936
Securities held-to-maturity, before Residential mortgage-backed securities	10,936
Securities held-to-maturity, at amortized cost	10,936
Securities held-to-maturity, After 10 years, Fair Value	10,819
Securities held-to-maturity, before Residential mortgage-backed securities Fair Value	10,819
Securities held to maturity, Fair Value	10,819
Residential Mortgage-Backed Securities
Securities available-for-sale
Securities available-for-sale, Residential mortgage-backed securities	615,955	346,001
Securities available-for-sale
Securities available-for-sale, Fair Value	$ 617,253	$ 350,597

Available for sale debt securities amortized cost basis before residential mortgage-backed securities.

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Available for sale securities before residential mortgage backed securities.

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Held-to-maturity debt securities amortized cost basis before residential mortgage backed securities.

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Held to maturity securities before residential mortgage backed securities.

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

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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.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity) with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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