Loans and Allowance for Credit Losses - Credit impaired loans acquired during the period (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments receivable on PCI loans at acquisition:	$ 6,954,000	$ 5,717,000
Cash flows expected to be collected at acquisition	1,070,000	3,715,000
Purchased credit impaired loans	6,366,000	5,269,000
Related Allowance	36,000	307,000
Purchased Credit Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments receivable on PCI loans at acquisition:	0	982,000
Purchased credit impaired loans	383,000	612,000
Related Allowance	0	0
Fair value of acquired loans at acquisition	0	631,000
Commercial | Purchased Credit Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments receivable on PCI loans at acquisition:	0	982,000
Cash flows expected to be collected at acquisition	0	693,000
Purchased credit impaired loans	$ 383,000	$ 612,000