Investment Securities - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	$ 693,745	$ 90,766
AAA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	479,507	83,095
AA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	209,739	7,671
A
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	1,080
BBB
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	3,000
Not Rated
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	419
U.S. Treasury and U.S. government agencies
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	18,820	25,565
U.S. Treasury and U.S. government agencies | AAA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	18,820	25,565
U.S. Treasury and U.S. government agencies | AA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0	0
U.S. Treasury and U.S. government agencies | A
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
U.S. Treasury and U.S. government agencies | BBB
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
U.S. Treasury and U.S. government agencies | Not Rated
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Mortgage-backed securities, residential
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	343,866	39,276
Mortgage-backed securities, residential | AAA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	343,866	39,276
Mortgage-backed securities, residential | AA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0	0
Mortgage-backed securities, residential | A
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Mortgage-backed securities, residential | BBB
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Mortgage-backed securities, residential | Not Rated
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Collateralized mortgage obligations, residential
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	8,488	14,590
Collateralized mortgage obligations, residential | AAA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	8,488	14,590
Collateralized mortgage obligations, residential | AA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0	0
Collateralized mortgage obligations, residential | A
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Collateralized mortgage obligations, residential | BBB
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Collateralized mortgage obligations, residential | Not Rated
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Mortgage-backed securities, multifamily
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	2,724	705
Mortgage-backed securities, multifamily | AAA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	2,724	705
Mortgage-backed securities, multifamily | AA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0	0
Mortgage-backed securities, multifamily | A
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Mortgage-backed securities, multifamily | BBB
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Mortgage-backed securities, multifamily | Not Rated
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Obligations of states and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	316,847	10,630
Obligations of states and political subdivisions | AAA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	105,609	2,959
Obligations of states and political subdivisions | AA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	209,739	$ 7,671
Obligations of states and political subdivisions | A
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	1,080
Obligations of states and political subdivisions | BBB
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Obligations of states and political subdivisions | Not Rated
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	419
Corporate bonds
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	3,000
Corporate bonds | AAA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Corporate bonds | AA
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Corporate bonds | A
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	0
Corporate bonds | BBB
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	3,000
Corporate bonds | Not Rated
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Total securities	$ 0