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Depreciation Expense Related to Property and Equipment (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Property Plant And Equipment [Abstract]        
Depreciation Expense $ 371 $ 445 $ 739 $ 886