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Fair Value Measurement - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Fair Value Disclosures [Abstract]    
Transfers between level 1 to level 2, Assets $ 0 $ 0
Transfers between level 2 to level 1, Assets 0 0
Transfers between level 1 to level 2, Liabilities 0 0
Transfers between level 2 to level 1, Liabilities 0 0
Transfer into level 3 0 0
Transfer out of level 3 0 $ 0
Carrying value of loans fully charged-off $ 0