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Financial Instruments (Bonds) - Additional Information (Detail) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2016
Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]    
Corporate and municipal bonds $ 41.6 $ 40.8
Maturity dates of bonds, start date 2016-04  
Maturity dates of bonds, end date 2021-10