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Fair Value Measurement - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2021
Dec. 31, 2020
Fair Value Measurement [Line Items]    
Carrying value of debt $ 243,872 $ 270,359
Restricted investments 21,700 23,400
Fixed-rate Borrowings [Member]    
Fair Value Measurement [Line Items]    
Increase (decrease) in fair value of debt 4,100 6,100
Carrying value of debt $ 243,900 $ 270,400