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Revolving Credit Facilities - Information Regarding Company's Revolving Credit Facilities (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Debt Instrument [Line Items]    
Carrying Amount $ 5,000 $ 100,000
Revolving Credit Facility [Member] | Unsecured Debt [Member] | J.P. Morgan Chase Bank, N.A. and Wells Fargo Securities, LLC [Member]    
Debt Instrument [Line Items]    
Carrying Amount $ 5,000 $ 100,000
Weighted-Average Interest Rate 2.70% 3.70%
Lines of Credit Maturity Date 2024-01  
Revolving Credit Facility [Member] | Unsecured Debt [Member] | PNC Bank National Association [Member]    
Debt Instrument [Line Items]    
Carrying Amount $ 0 $ 0
Lines of Credit Maturity Date 2024-01