Loans, Allowance for Credit Losses and Impaired Loans - Acquired loans (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, before Fees, Gross	$ 647,608,000		$ 647,608,000		$ 633,903,000
Carrying amount	639,649,000		639,649,000		625,513,000
Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, before Fees, Gross	102,878,000		102,878,000		112,032,000
Carrying amount	101,985,000		101,985,000		110,705,000
PCI loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, before Fees, Gross	1,424,000		1,424,000		1,692,000
Carrying amount	1,045,000		1,045,000		1,110,000
Changes in accretable yield under ASC 310-20:
Accretion	(28,000)	$ (32,000)	(56,000)	$ (32,000)
Non-accretable yield on purchase credit impaired loans	323,000		323,000		463,000
Non PCI loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, before Fees, Gross	101,454,000		101,454,000		110,340,000
Carrying amount	100,940,000		100,940,000		109,595,000
Changes in accretable yield under ASC 310-20:
Balance at beginning of period			745,000
Acquisitions					1,703,000
Accretion			(231,000)		(958,000)
Balance at end of period	$ 514,000		$ 514,000		$ 745,000