Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Summary of Company's Long-Term Debt Instruments at their Carrying Value and Fair Value (Detail)

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Financial Instruments - Summary of Company's Long-Term Debt Instruments at their Carrying Value and Fair Value (Detail) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Debt Instrument [Line Items]    
Carrying value $ 187,033 $ 171,175
Fair value 198,621 189,363
Unsecured Debentures    
Debt Instrument [Line Items]    
Carrying value 55,455 54,905
Fair value 56,305 53,830
Secured Notes    
Debt Instrument [Line Items]    
Carrying value 130,217 115,350
Fair value 141,230 134,609
Other Long Term Debt    
Debt Instrument [Line Items]    
Carrying value 1,361 920
Fair value $ 1,086 $ 924