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Valuation And Qualifying Accounts (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Allowance for Doubtful Accounts      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at the beginning of the period $ 3,181 $ 3,825 $ 4,412
Additions [1] 2,269 224 884
Deduction (1,260) (868) (1,471)
Balance at the end of the period 4,190 3,181 3,825
Valuation Allowance of Deferred Tax Assets      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at the beginning of the period 832 1,984 2,311
Additions [1] 183 20 75
Deduction 0 (1,172) (402)
Balance at the end of the period $ 1,015 $ 832 $ 1,984
[1] Reductions in/charges to revenues and expenses.