Securities - Fair Value and Age of Gross Unrealized Losses of Debt Securities (Details) $ in Thousands	Sep. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months \| security	22	3
Fair Value, Less Than 12 Months	$ 286,466	$ 36,196
Unrealized Losses, Less Than 12 Months	$ (3,070)	$ (90)
Number of Securities, 12 Months or More \| security	0	0
Fair Value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of Securities, Total \| security	22	3
Fair Value, Total	$ 286,466	$ 36,196
Unrealized Losses, Total	$ (3,070)	$ (90)
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months \| security	4	0
Fair Value, Less Than 12 Months	$ 43,200	$ 0
Unrealized Losses, Less Than 12 Months	$ (248)	$ 0
Number of Securities, 12 Months or More \| security	0	0
Fair Value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of Securities, Total \| security	4	0
Fair Value, Total	$ 43,200	$ 0
Unrealized Losses, Total	$ (248)	$ 0
Obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months \| security	0	0
Fair Value, Less Than 12 Months	$ 0	$ 0
Unrealized Losses, Less Than 12 Months	$ 0	$ 0
Number of Securities, 12 Months or More \| security	0	0
Fair Value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of Securities, Total \| security	0	0
Fair Value, Total	$ 0	$ 0
Unrealized Losses, Total	$ 0	$ 0
Collateralized mortgage obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months \| security	7	2
Fair Value, Less Than 12 Months	$ 88,290	$ 35,697
Unrealized Losses, Less Than 12 Months	$ (1,198)	$ (89)
Number of Securities, 12 Months or More \| security	0	0
Fair Value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of Securities, Total \| security	7	2
Fair Value, Total	$ 88,290	$ 35,697
Unrealized Losses, Total	$ (1,198)	$ (89)
Residential mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months \| security	3	0
Fair Value, Less Than 12 Months	$ 48,497	$ 0
Unrealized Losses, Less Than 12 Months	$ (966)	$ 0
Number of Securities, 12 Months or More \| security	0	0
Fair Value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of Securities, Total \| security	3	0
Fair Value, Total	$ 48,497	$ 0
Unrealized Losses, Total	$ (966)	$ 0
Commercial mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months \| security	7	0
Fair Value, Less Than 12 Months	$ 101,479	$ 0
Unrealized Losses, Less Than 12 Months	$ (658)	$ 0
Number of Securities, 12 Months or More \| security	0	0
Fair Value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of Securities, Total \| security	7	0
Fair Value, Total	$ 101,479	$ 0
Unrealized Losses, Total	$ (658)	$ 0
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months \| security	0	1
Fair Value, Less Than 12 Months	$ 0	$ 499
Unrealized Losses, Less Than 12 Months	$ 0	$ (1)
Number of Securities, 12 Months or More \| security	0	0
Fair Value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of Securities, Total \| security	0	1
Fair Value, Total	$ 0	$ 499
Unrealized Losses, Total	$ 0	$ (1)
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months \| security	1	0
Fair Value, Less Than 12 Months	$ 5,000	$ 0
Unrealized Losses, Less Than 12 Months	$ 0	$ 0
Number of Securities, 12 Months or More \| security	0	0
Fair Value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of Securities, Total \| security	1	0
Fair Value, Total	$ 5,000	$ 0
Unrealized Losses, Total	$ 0	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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