Annual report pursuant to Section 13 and 15(d)

Qualified Affordable Housing Project Investments - Additional Information (Detail)

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Qualified Affordable Housing Project Investments - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Investments in Affordable Housing Projects [Line Items]    
Qualified affordable housing project investments $ 7,800,000 $ 9,600,000
Unfunded commitments related to investments $ 84,000 112,000
Investment commitments expected to be paid 2023  
Income Tax Expense    
Investments in Affordable Housing Projects [Line Items]    
Qualified affordable housing project investments, amortization expense recognized $ 1,800,000 $ 2,000,000.0