Federal Home Loan Bank Advances - Summary of Federal Home Loan Bank Advances (Detail) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Advance Amount		$ 30,000,000
Federal Home Loan Bank Advances [Member] \| Federal Home Loan Bank Advances with 2.53 Interest Rate [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Advance Amount		20,000,000
Interest Rate	2.53%
Final Maturity	Jan. 09, 2018
Federal Home Loan Bank Advances [Member] \| Federal Home Loan Bank Advances with 1.6 Interest Rate [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Advance Amount		$ 10,000,000
Interest Rate	1.60%
Final Maturity	Jan. 05, 2018

Including both current and noncurrent portions, Federal Home Loan Bank borrowings initially due beyond one year or beyond the normal operating cycle if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64702-112823

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

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