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Short-Term Borrowings - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended 12 Months Ended
Aug. 31, 2018
Mar. 31, 2020
Dec. 31, 2019
Aug. 09, 2018
Aug. 08, 2018
Line Of Credit Facility [Line Items]          
Fund-based and non-fund-based credit facilities limits available   $ 13,989,000 $ 14,307,000    
Utilization of credit facility for non fund-based usage   7,292,000 7,486,000    
Credit facility, amount utilized   167,639,000 72,098,000    
Short-term borrowings   $ 165,000,000 $ 70,000,000    
Revolving credit facility, expiration month and year   Aug. 08, 2023      
Margin over LIBOR 1.375% 1.375% 1.375%    
Percentage of commitment fee   0.20% 0.20%    
Revolving Credit Facility          
Line Of Credit Facility [Line Items]          
Credit facility, maximum borrowing capacity       $ 500,000,000 $ 350,000,000
Non-Fund-Based Credit Facility          
Line Of Credit Facility [Line Items]          
Credit facility, amount utilized   $ 2,639,000 $ 2,098,000    
Fund-Based Credit Facility          
Line Of Credit Facility [Line Items]          
Margin over LIBOR   1.375% 1.375%