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Valuation And Qualifying Accounts (Detail) - Allowance for Doubtful Accounts - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at beginning of period $ 25 $ 25  
Additions   0 $ 25
Deduction $ 25 0  
Balance at end of period   $ 25 $ 25