Loans Held for Investment and Allowance for Loan Losses - Recorded Investment in Impaired Loans and Related Valuation Allowance (Detail) - USD ($)		Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Receivables [Abstract]
Recorded Investment	[1]	$ 39,320,000	$ 24,582,000	$ 26,408,000
Valuation Allowance		$ 3,046,000	$ 3,228,000	$ 3,866,000

[1] Includes $7,275,000, $464,000 and $251,000 of purchased credit impaired loans as of June 30, 2020 and 2019, and December 31, 2019, respectively.