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Fair Value Information - Additional Information (Detail) - USD ($)
Jun. 30, 2019
Dec. 31, 2018
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]    
Fair value assets transfers from Level 1 to Level 2 $ 0 $ 0
Fair value assets transfers from Level 2 to Level 1 0 0
Fair value liabilities transfers from Level 1 to Level 2 0 0
Fair value liabilities transfers from Level 2 to Level 1 $ 0 $ 0