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Financial Instruments - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Financial Instruments [Line Items]      
Period cash equivalents and short-term investments have been in continuous unrealized loss position, years, maximum 1 year    
CCKF [Member]      
Financial Instruments [Line Items]      
Non controlling interest $ 3.2    
Percentage of investment in equity affiliate 30.70%    
Loss from investment in affiliate $ (0.3) $ (0.9) $ (0.3)