Commitments and Contingencies - Schedule of Financial Instruments Representing Credit Risk (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Unused commitments to extend credit	$ 622,212	$ 584,494
Standby letters of credit	11,526	11,552
Total	$ 633,738	$ 596,046

Fair value portion of guarantee, including, but not limited to, financial standby letter of credit, fair value guarantee, guarantee of collection of scheduled contractual cash flows from financial assets, and contracts that contingently require the guarantor to make payments or perform services.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115931803&loc=d3e12201-110248

Name:	us-gaap_GuaranteesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant