Disclosures about Fair Value of Financial Instruments - Statement of Changes in Level 3 Assets Measured at Fair Value on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring - Significant Unobservable Inputs (Level 3) - Residential Mortgage [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at December 31,	$ 69	$ 60
Issuances	451	407
Settlements	(441)	(398)
Balance at December 31,	$ 79	$ 69