Fair Value Disclosures - Summary of Loans Held-for-Sale at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Fair Value Measurements Loans Held For Sale [Abstract]
Unpaid principal balance on loans held-for-sale	$ 44,784	$ 76,602	$ 91,091
Net unrealized gains on loans held-for-sale	1,297	2,983	3,575
Loans held-for-sale at fair value	$ 46,081	$ 79,585	$ 94,666