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Employee Benefit Plans and Similar Obligations - Summary of Share Based Compensation Plan (Plan 2018-2021) (Parenthetical) (Detail) - Plan 2018-2021 [member]
12 Months Ended
Dec. 31, 2018
Bottom of range [member]  
Disclosure of terms and conditions of share-based payment arrangement [line items]  
Average remaining life of plan 7 months
Top of range [member]  
Disclosure of terms and conditions of share-based payment arrangement [line items]  
Average remaining life of plan 31 months