Fair Value of Assets and Liabilities - Summary of Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (Detail) - USD ($)	Sep. 30, 2020		Jun. 30, 2020	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Assets
Impaired loans	$ 107,809,000			$ 113,581,000
Loan collateral in process of foreclosure	48,742,000	[1]	$ 47,375,000	52,711,000	[1]	$ 53,539,000	$ 52,368,000	$ 49,495,000
Fair Value, Measurements, Nonrecurring [Member]
Assets
Equity investments	10,284,000			10,079,000
Impaired loans	114,741,000			34,915,000
Loan collateral in process of foreclosure	48,742,000			52,711,000
Total	173,767,000			97,705,000
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Assets
Equity investments	10,284,000			10,079,000
Impaired loans	114,741,000			34,915,000
Loan collateral in process of foreclosure	48,742,000			52,711,000
Total	$ 173,767,000			$ 97,705,000

[1] Includes financed sales of this collateral to third parties that are reported separately from the loan portfolio, and that are conducted by the Bank of $9,701 as of September 30, 2020 and $8,163 as of December 31, 2019.