Loans and Allowance for Loan Losses - Financial Effect of TDRs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($) loan	Dec. 31, 2015 USD ($) loan
Financing Receivable Modifications [Line Items]
Number of loans | loan	7	9	16
Pre-modification outstanding recorded investment	$ 1,883	$ 1,966	$ 3,546
Post-modification outstanding recorded investment	1,883	$ 1,966	3,546
Charge offs and specific reserves	$ 76		$ 132
Consumer and Other
Financing Receivable Modifications [Line Items]
Number of loans | loan	1	3
Pre-modification outstanding recorded investment	$ 25	$ 29
Post-modification outstanding recorded investment	$ 25	$ 29
Commercial and Industrial
Financing Receivable Modifications [Line Items]
Number of loans | loan	2		6
Pre-modification outstanding recorded investment	$ 627		$ 2,301
Post-modification outstanding recorded investment	$ 627		2,301
Charge offs and specific reserves			$ 86
Commercial Real Estate | Owner Occupied
Financing Receivable Modifications [Line Items]
Number of loans | loan	1	1	4
Pre-modification outstanding recorded investment	$ 377	$ 118	$ 786
Post-modification outstanding recorded investment	$ 377	$ 118	$ 786
Commercial Real Estate | Non-Owner Occupied
Financing Receivable Modifications [Line Items]
Number of loans | loan	2		1
Pre-modification outstanding recorded investment	$ 711		$ 133
Post-modification outstanding recorded investment	711		133
Charge offs and specific reserves	$ 68		1
Residential Real Estate
Financing Receivable Modifications [Line Items]
Charge offs and specific reserves			$ 45
Residential Real Estate | 1-to-4 Family Mortgage
Financing Receivable Modifications [Line Items]
Number of loans | loan	1	5	5
Pre-modification outstanding recorded investment	$ 143	$ 1,819	$ 326
Post-modification outstanding recorded investment	143	$ 1,819	326
Charge offs and specific reserves	$ 8		$ 45