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Fair Value of Financial Instruments - Summary of Changes in Fair Value of Investments (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Fair Value Disclosures [Abstract]    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales $ (38) $ 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning Balance 803 686
Purchases and adjustments 9 6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 (57) 0
Investment Income 4 3
Ending Balance $ 835 $ 695