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Derivative Instruments - Terms of Interest Rate Swaps Underlying Swaption (Parenthetical) (Detail) - USD ($)
Jul. 31, 2026
Jan. 31, 2026
Oct. 31, 2024
Jul. 31, 2018
Jan. 31, 2018
Apr. 30, 2017
Interest rate swaption agreements [Member] | Scenario Forecast [Member]            
Derivative [Line Items]            
Principal amount $ 82,500,000 $ 82,500,000 $ 85,400,000 $ 160,000,000 $ 160,000,000 $ 155,000,000