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Investments - Summary of Equity Investments (Detail) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]    
Investment in equities $ 16,911 $ 0
Cost Method of Accounting [Member]    
Schedule Of Available For Sale Securities [Line Items]    
Investment in equities 15,066  
Available for sale method [Member]    
Schedule Of Available For Sale Securities [Line Items]    
Investment in equities $ 1,845