Commitments, Contingencies and Credit Risk - Financial Instruments Whose Contractual Amounts Represent Credit Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Contractual amounts represent credit risk	$ 104,528	$ 94,798
Commitments to Grant Mortgage Loans
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Contractual amounts represent credit risk	52,017	54,423
Unfunded Commitments Under Lines of Credit
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Contractual amounts represent credit risk	44,752	33,641
Standby Letters of Credit
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Contractual amounts represent credit risk	$ 7,759	$ 6,734

This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(19))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(17))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(25))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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