Fair Values of Assets and Liabilities - Summary of Changes in Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - Fair Value, Inputs, Level 3 [Member] - Fair Value, Measurements, Recurring [Member] - Mortgage-backed securities [Member] - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Beginning Balance	[1]	$ 397	$ 479
Included in net income	[1]	(68)	(85)
Ending Balance	[1]	$ 329	$ 394

[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.