Loans and Allowance for Loan Losses - ALL by Loan Classification (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 4,964	$ 4,354	$ 3,880
All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	4,964	4,354
Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Performing [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	4,932	4,096
Impaired Loans [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	32	258
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	2,246	1,906	1,734
Commercial Real Estate [Member] | Performing [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	2,246	1,906
Commercial Real Estate [Member] | Impaired Loans [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	1,243	1,015	906
Consumer Real Estate [Member] | Performing [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	1,243	1,015
Consumer Real Estate [Member] | Impaired Loans [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	861	627	690
Construction and Land Development [Member] | Performing [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	861	627
Construction and Land Development [Member] | Impaired Loans [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	576	777	524
Commercial and Industrial [Member] | Performing [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	544	519
Commercial and Industrial [Member] | Impaired Loans [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	32	258
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	38	29	$ 26
Consumer and Other [Member] | Performing [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	38	29
Consumer and Other [Member] | Impaired Loans [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0	$ 0