Income Taxes - Additional Information (Detail) - USD ($)		12 Months Ended
	Jul. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Adjustment To Deferred Tax Asset For Change In State Tax Law	$ 943,000	$ 0	$ 943,000	$ 0
Net deferred tax assets		14,805,000	17,189,000
Tax Cuts and Jobs Act of 2017, change in tax rate, deferred tax asset, income tax expense (benefit)		1,300,000
Excise tax on real estate investment trust (REIT) dividend		$ 0	0	$ 1,945,000
Effective income tax rate reconciliation, change in enacted tax rate and excise tax on real estate investment trust dividend, amount			$ 602,000
Statutory federal rate		21.00%	21.00%	35.00%
Unrecognized tax benefits		$ 0	$ 0
Unrecognized tax benefits, income tax penalties and interest expense		0	$ 0
Highlands Bancorp, Inc.
Income Tax Disclosure [Line Items]
Net deferred tax assets		$ 4,300,000