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Summary of Significant Accounting Policies - Allowance for Doubtful Accounts and Other Accounts Receivable Allowances (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Allowance For Doubtful Accounts Receivable Rollforward      
Allowance, balance at the beginning $ 9,325 $ 9,654 $ 10,116
Provision charged to income 864 29 764
Accounts written off, net of recoveries (56) (358) (1,226)
Allowance, balance at ending $ 10,133 $ 9,325 $ 9,654