Securities Held-to-Maturity - Schedule of Maturity Profile of Securities Held-to-Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity due within one year
Held-to-maturity due one year through five years
Held-to-maturity due five years through ten years
Held-to-maturity due over ten years	411	451
Held-to-maturity cost or amortized cost	$ 411	$ 451