Disclosures about Fair Value of Financial Instruments - Narrative (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale, average life from purchase to sale (days)	30 days
Unrealized gain (loss) on investment securities	$ 1,299	$ (1,634)	$ 0
Interest-only GNMA securities | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss) on investment securities	600
Cash settlements	$ 1,500