v3.19.3.a.u2
Revenue - Additional Information (Detail)
$ in Millions
 12 Months Ended
Dec. 31, 2019
USD ($)
Schedule of Investment Advisory Administration Fees and Securities Lending Revenue and Performance Fees by Type [line Items]  
Estimated annual fixed minimum fees for currently outstanding contracts $ 640
Minimum [Member]  
Schedule of Investment Advisory Administration Fees and Securities Lending Revenue and Performance Fees by Type [line Items]  
Term of currently outstanding contracts 1 year
Maximum [Member]  
Schedule of Investment Advisory Administration Fees and Securities Lending Revenue and Performance Fees by Type [line Items]  
Term of currently outstanding contracts 5 years