Loans and Allowance for Loan Losses - Narrative (Details)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended	45 Months Ended
	Dec. 31, 2013 USD ($)	Sep. 30, 2017 USD ($) contract property method component	Sep. 30, 2016 USD ($) contract	Sep. 30, 2017 USD ($) contract property category method component loan quarter	Sep. 30, 2016 USD ($) contract	Dec. 31, 2016 USD ($)	Sep. 30, 2017 USD ($) property method component
Financing Receivable, Impaired [Line Items]
Net deferred fees		$ 667,000	$ 796,000	$ 667,000	$ 796,000		$ 667,000
Allowance for loan losses, number of evaluation components | component		2		2			2
Increase (decrease) in allowance for loan losses				$ 168,000
Number of rolling quarters utilized in charge-off factor calculation | quarter				12
Liability for unfunded commitments		$ 284,000		$ 284,000		$ 284,000,000	$ 284,000
Total valuation methods used on impaired loans | method		3		3			3
Impaired loans, identified during the period				$ 3,000,000
Impaired loans, principal curtailment				752,000
Impaired loans, partial charge-offs				395,000
Impaired loans, reclassification to other real estate				1,000,000
Impaired loans, reclassification to performing loans				$ 150,000
Number of points in internal risk rating system | category				9
Number of categories in internal risk rating system considered as not criticized | category				6
Commercial relationship credit review threshold amount		$ 1,000,000		$ 1,000,000			$ 1,000,000
Past due period before loans placed in non-accrual status				90 days
Recent loan payment history before removal from non-accrual status				6 months
Number of Contracts | contract		1		1
Commercial
Financing Receivable, Impaired [Line Items]
Loans acquired, purchase price	$ 74,300,000
Premium on loans acquired ratio	1.024
Loans acquired, premium paid	$ 1,800,000
Loans acquired, outstanding balance		$ 19,900,000		$ 19,900,000		$ 20,500,000	19,900,000
Loans acquired, outstanding balance, decrease							54,400,000
Loans acquired, refinanced							19,600,000
Loans acquired, sold in participation							10,500,000
Loans acquired, sold back to institution							9,700,000
Loans acquired, amortization							7,100,000
Loans acquired, principal paydowns							$ 7,500,000
Loans acquired, remaining portfolio, weighted average yield		5.46%		5.46%			5.46%
Residential
Financing Receivable, Impaired [Line Items]
Concentration risk, percentage				56.00%
Number foreclosed properties held | property		9		9			9
Foreclosed properties held		$ 777,000		$ 777,000			$ 777,000
Consumer
Financing Receivable, Impaired [Line Items]
Number of additional collateralized loans in the process of foreclosure | loan				5
Investment in loans in the process of foreclosure		378,000		$ 378,000			378,000
Investment in loans in the process of foreclosure, related allowance		$ 0		0			$ 0
Total Recorded Investment In Impaired Financing Receivables | Credit Concentration Risk
Financing Receivable, Impaired [Line Items]
Decrease in impaired loans				$ 573,000
Concentration risk, percentage				4.70%
Troubled Debt Restructured Loans
Financing Receivable, Impaired [Line Items]
Number of Contracts | contract			0		0
Troubled Debt Restructured Loans | Portfolio Risk | Accruing
Financing Receivable, Impaired [Line Items]
Concentration risk, percentage				48.00%		49.00%
Troubled Debt Restructured Loans | Portfolio Risk | Commercial | Accruing
Financing Receivable, Impaired [Line Items]
Number of Contracts | contract		1		1
Troubled Debt Restructured Loans | Portfolio Risk | Commercial | Accruing | Acquisition & Development
Financing Receivable, Impaired [Line Items]
Number of Contracts | contract		0		0
Troubled Debt Restructured Loans | Portfolio Risk | Residential | Accruing
Financing Receivable, Impaired [Line Items]
Number of Contracts | contract		0		0
Troubled Debt Restructured Loans | Portfolio Risk | Consumer | Accruing
Financing Receivable, Impaired [Line Items]
Number of Contracts | contract		0		0