Securities - Amortized cost and fair value (Details) $ in Thousands	9 Months Ended
Sep. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Securities available-for-sale:
Amortized Cost	$ 145,129	$ 120,215
Gross unrealized gains	1,772	3,504
Gross unrealized losses	(752)	(157)
Fair value	146,149	123,562
Securities held to maturity:
Held-to-maturity, Amortized Cost	6,406	6,510
Held-to-maturity, Gross Unrealized Gains	254	347
Fair Value	$ 6,660	$ 6,857
Number of securities in unrealized loss positions \| security	51	14
Number of securities deemed other-than-temporarily impaired \| security	0
Securities pledged as collateral fair value	$ 63,600	$ 55,900
U.S. asset backed securities
Securities available-for-sale:
Amortized Cost	21,120	25,303
Gross unrealized gains	199	364
Gross unrealized losses	(26)	(75)
Fair value	$ 21,293	$ 25,592
Securities held to maturity:
Number of securities in unrealized loss positions \| security	4	8
U.S. government agency mortgage-backed securities
Securities available-for-sale:
Amortized Cost	$ 5,351	$ 3,854
Gross unrealized gains	137	192
Gross unrealized losses	(29)
Fair value	$ 5,459	4,046
Securities held to maturity:
Number of securities in unrealized loss positions \| security	1
U.S. government agency collateralized mortgage obligations
Securities available-for-sale:
Amortized Cost	$ 23,712	23,010
Gross unrealized gains	483	916
Gross unrealized losses	(142)	(17)
Fair value	$ 24,053	$ 23,909
Securities held to maturity:
Number of securities in unrealized loss positions \| security	7	1
State and municipal securities
Securities available-for-sale:
Amortized Cost	$ 72,415	$ 63,848
Gross unrealized gains	874	2,025
Gross unrealized losses	(461)	(63)
Fair value	72,828	65,810
Securities held to maturity:
Held-to-maturity, Amortized Cost	6,406	6,510
Held-to-maturity, Gross Unrealized Gains	254	347
Fair Value	$ 6,660	$ 6,857
Number of securities in unrealized loss positions \| security	23	3
U.S. Treasuries
Securities available-for-sale:
Amortized Cost	$ 15,082
Gross unrealized gains	6
Gross unrealized losses	(78)
Fair value	$ 15,010
Securities held to maturity:
Number of securities in unrealized loss positions \| security	11
Non-U.S. government agencies collateralized mortgage obligations
Securities available-for-sale:
Amortized Cost	$ 999
Fair value	$ 999
Securities held to maturity:
Number of securities in unrealized loss positions \| security	1
Corporate bonds
Securities available-for-sale:
Amortized Cost	$ 6,450	$ 4,200
Gross unrealized gains	73	7
Gross unrealized losses	(16)	(2)
Fair value	$ 6,507	$ 4,205
Securities held to maturity:
Number of securities in unrealized loss positions \| security	4	2

The number of securities deemed to be other-than-temporarily impaired.

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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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).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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The sum of the fair values, as of the date of each statement of financial position presented, of securities that are restricted as collateral for the payment of related debt obligations, primarily secured borrowings and repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

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