Loans, Allowance for Credit Losses and Impaired Loans - Loan Impairment and Allowance for Credit Losses (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	$ 7,063,000	$ 7,024,000	$ 7,063,000	$ 6,703,000
Charge-offs	(456,000)	(283,000)	(797,000)	(374,000)
Recoveries	159,000	80,000	200,000	242,000
Provision for credit losses	300,000	275,000	600,000	525,000
Loans and Leases Receivable, Allowance, Ending Balance	7,066,000	7,096,000	7,066,000	7,096,000
Individually evaluated for impairment: Balance in allowance	598,000		598,000		$ 1,042,000
Individually evaluated for impairment: Related loan balance	18,856,000		18,856,000		25,454,000
Collectively evaluated for impairment: Balance in allowance	6,468,000		6,468,000		6,021,000
Collectively evaluated for impairment: Related loan balance	627,859,000		627,859,000		607,122,000
Unamortized discounts on acquired loans	893,000		893,000		1,327,000
Other real estate secured
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	4,295,000	4,249,000	4,276,000	3,858,000
Charge-offs	(220,000)	(204,000)	(421,000)	(204,000)
Recoveries	8,000	3,000	13,000	68,000
Provision for credit losses	276,000	386,000	491,000	712,000
Loans and Leases Receivable, Allowance, Ending Balance	4,359,000	4,434,000	4,359,000	4,434,000
Individually evaluated for impairment: Balance in allowance	164,000		164,000		278,000
Individually evaluated for impairment: Related loan balance	13,851,000		13,851,000		14,947,000
Collectively evaluated for impairment: Balance in allowance	4,195,000		4,195,000		3,998,000
Collectively evaluated for impairment: Related loan balance	422,082,000		422,082,000		410,527,000
1 - 4 Family residential secured
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	1,644,000	1,802,000	1,643,000	1,744,000
Charge-offs	(193,000)	(8,000)	(198,000)	(52,000)
Recoveries	139,000	55,000	141,000	124,000
Provision for credit losses	(247,000)	38,000	(243,000)	71,000
Loans and Leases Receivable, Allowance, Ending Balance	1,343,000	1,887,000	1,343,000	1,887,000
Individually evaluated for impairment: Balance in allowance	265,000		265,000		586,000
Individually evaluated for impairment: Related loan balance	4,574,000		4,574,000		8,775,000
Collectively evaluated for impairment: Balance in allowance	1,078,000		1,078,000		1,057,000
Collectively evaluated for impairment: Related loan balance	141,703,000		141,703,000		137,192,000
Other
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	667,000	514,000	654,000	536,000
Charge-offs	(43,000)	(71,000)	(178,000)	(118,000)
Recoveries	12,000	22,000	46,000	50,000
Provision for credit losses	(2,000)	(21,000)	112,000	(24,000)
Loans and Leases Receivable, Allowance, Ending Balance	634,000	444,000	634,000	444,000
Individually evaluated for impairment: Balance in allowance	169,000		169,000		178,000
Individually evaluated for impairment: Related loan balance	431,000		431,000		1,732,000
Collectively evaluated for impairment: Balance in allowance	465,000		465,000		476,000
Collectively evaluated for impairment: Related loan balance	64,074,000		64,074,000		59,403,000
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	457,000	459,000	490,000	565,000
Provision for credit losses	273,000	(128,000)	240,000	(234,000)
Loans and Leases Receivable, Allowance, Ending Balance	730,000	$ 331,000	730,000	$ 331,000
Collectively evaluated for impairment: Balance in allowance	$ 730,000		$ 730,000		$ 490,000