Fair Values of Assets and Liabilities - Summary of Significant Unobservable Inputs used in Level 3 Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Inputs, Level 3 [Member] - Fair Value, Measurements, Recurring [Member] $ in Thousands		6 Months Ended
		Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Mortgage-backed securities [Member]
Mortgage Servicing Rights	[1]		$ 329	$ 397	$ 394	$ 479
Prepayment Rate [Member] | Mortgage-backed securities [Member]
Servicing Asset, Valuation Technique [Extensible List]		us-gaap:ValuationTechniqueDiscountedCashFlowMember		us-gaap:ValuationTechniqueDiscountedCashFlowMember
Mortgage Servicing Rights		$ 329		$ 397
Minimum [Member] | Prepayment Rate [Member]
Mortgage Servicing Rights, Measuring Inputs		9.88
Minimum [Member] | Discount Rate [Member]
Mortgage Servicing Rights, Measuring Inputs		9.00
Minimum [Member] | Delinquency Rate [Member]
Mortgage Servicing Rights, Measuring Inputs		2.33
Minimum [Member] | Default Rate [Member]
Mortgage Servicing Rights, Measuring Inputs		0.08
Maximum [Member] | Prepayment Rate [Member]
Mortgage Servicing Rights, Measuring Inputs		29.13
Maximum [Member] | Discount Rate [Member]
Mortgage Servicing Rights, Measuring Inputs		9.00
Maximum [Member] | Delinquency Rate [Member]
Mortgage Servicing Rights, Measuring Inputs		2.90
Maximum [Member] | Default Rate [Member]
Mortgage Servicing Rights, Measuring Inputs		0.14
Weighted Average [Member] | Prepayment Rate [Member]
Mortgage Servicing Rights, Measuring Inputs	[2]	18.57		13.08
Fair value valuation techniques		Prepayment Rate
Weighted Average [Member] | Discount Rate [Member]
Mortgage Servicing Rights, Measuring Inputs	[2]	9.00		9.50
Fair value valuation techniques		Discount Rate
Weighted Average [Member] | Delinquency Rate [Member]
Mortgage Servicing Rights, Measuring Inputs	[2]	2.47		2.48
Fair value valuation techniques		Delinquency Rate
Weighted Average [Member] | Default Rate [Member]
Mortgage Servicing Rights, Measuring Inputs	[2]	0.12		0.09
Fair value valuation techniques		Default Rate

[1] Realized and unrealized gains and losses related to mortgage servicing rights are reported as a component of mortgage banking income in the Company’s consolidated statements of income.

[2] Unobservable inputs for mortgage servicing rights were weighted by loan amount.