Nature of Operations and Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018 USD ($) Entity	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Number of entities | Entity	2
Federal Statutory Income Tax Rate	21.00%	35.00%	35.00%
Tax Cuts And Jobs Act Of 2017 Change In Tax Rate Income Tax Expense (Benefit)		$ 1,086,000
Tax Cuts and Jobs Act of 2017, Re-measured net deferred tax assets		1,086,000
Tax Cuts and Jobs Act of 2017, Re-measured net deferred tax assets relating to unrealized losses on securities		535,000
Tax Cuts and Jobs Act of 2017, Stranded Tax Effect		535,000
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings		535,000
Interest or penalties incurred	$ 0	$ 0	$ 1,000
ASU 2016-02 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Operating right of use assets	3,251,000
Operating lease liabilities	3,251,000
ASU 2017-08 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Reduction in amortized cost of investment securities and retained earnings	1,385,000
ASU 2018-15 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Capitalizing of implementation costs	$ 311,000
Minimum [Member] | Core Deposits [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Estimated useful lives of core deposits	7 years
Maximum [Member] | Core Deposits [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Estimated useful lives of core deposits	10 years
Buildings and Improvements [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Estimated useful lives	39 years
Furniture and Fixtures [Member] | Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Estimated useful lives	4 years
Furniture and Fixtures [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Estimated useful lives	7 years
Equipment [Member] | Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Estimated useful lives	4 years
Equipment [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Line Items]
Estimated useful lives	7 years