Investment Securities - Summary of Unrealized Loss Positions (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) security	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) security	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) security
Investments in an unrealized loss position
Carrying value of securities pledged	$ 119,500,000		$ 119,500,000
Amount of pretax loss if securities in an unrealized loss position are sold	533,000		533,000
Less than 12 months, fair value	17,827,000		17,827,000		$ 31,931,000
Less than 12 months, unrealized loss	(303,000)		(303,000)		(276,000)
12 months or more, fair value	16,626,000		16,626,000		43,725,000
12 months or more, unrealized loss	(230,000)		(230,000)		$ (661,000)
Sales of debt securities, available-for-sale	30,900,000	$ 12,900,000	41,160,000	$ 26,616,000
Gain on sale of debt securities	554,000	47,000	830,000	80,000
Loss on sale of available-for-sale securities	0	97,000	0	248,000
Sales of equity securities	357,000	6,000,000.0	357,000	5,968,000
Gain on sale of equity securities	30,000	0	30,000	2,000
Loss on sale of equity securities	0	7,000	0	9,000
Sales of investment securities available-for-sale, unrealized holding gain	$ 3,000	$ 13,600,000	$ 17,000	$ 13,800,000
U. S. Agency securities
Investments in an unrealized loss position
Number of investments in an unrealized loss position | security	22		22		26
Less than 12 months, fair value	$ 4,652,000		$ 4,652,000		$ 8,160,000
Less than 12 months, unrealized loss	(74,000)		(74,000)		(59,000)
12 months or more, fair value	13,452,000		13,452,000		15,399,000
12 months or more, unrealized loss	$ (196,000)		$ (196,000)		$ (190,000)
U.S. Sponsored Mortgage-backed securities
Investments in an unrealized loss position
Number of investments in an unrealized loss position | security	9		9		40
Less than 12 months, fair value	$ 2,625,000		$ 2,625,000		$ 16,660,000
Less than 12 months, unrealized loss	(18,000)		(18,000)		(170,000)
12 months or more, fair value	3,174,000		3,174,000		27,498,000
12 months or more, unrealized loss	$ (34,000)		$ (34,000)		$ (454,000)
Municipal securities
Investments in an unrealized loss position
Number of investments in an unrealized loss position | security	9		9		13
Less than 12 months, fair value	$ 6,134,000		$ 6,134,000		$ 6,018,000
Less than 12 months, unrealized loss	(108,000)		(108,000)		(40,000)
12 months or more, fair value	0		0		828,000
12 months or more, unrealized loss	$ 0		$ 0		$ (17,000)
Other securities
Investments in an unrealized loss position
Number of investments in an unrealized loss position | security	5		5		2
Less than 12 months, fair value	$ 4,416,000		$ 4,416,000		$ 1,093,000
Less than 12 months, unrealized loss	(103,000)		(103,000)		(7,000)
12 months or more, fair value	0		0		0
12 months or more, unrealized loss	$ 0		$ 0		$ 0