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Revenue - Schedule of Estimated Investment Advisory, Administration Fees Expected to be Recognized in Future, Related to Unsatisfied Portion of Performance Obligations (Detail) - Investment Advisory, Administration Fees and Securities Lending Revenue [Member] - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Schedule of Investment Advisory Administration Fees and Performance Fees by Type [line Items]    
Revenue, Remaining Performance Obligation $ 367 $ 226
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-01-01    
Schedule of Investment Advisory Administration Fees and Performance Fees by Type [line Items]    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period   1 year
Revenue, Remaining Performance Obligation   $ 61
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01    
Schedule of Investment Advisory Administration Fees and Performance Fees by Type [line Items]    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period 1 year 1 year
Revenue, Remaining Performance Obligation $ 98 $ 53
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01    
Schedule of Investment Advisory Administration Fees and Performance Fees by Type [line Items]    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period 1 year 1 year
Revenue, Remaining Performance Obligation $ 88 $ 42
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01    
Schedule of Investment Advisory Administration Fees and Performance Fees by Type [line Items]    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period 1 year
Revenue, Remaining Performance Obligation $ 74 $ 70
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01    
Schedule of Investment Advisory Administration Fees and Performance Fees by Type [line Items]    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period  
Revenue, Remaining Performance Obligation $ 107