Related Parties Related Parties - Summary of Sub-allocation Assets (Details) - Apollo - Related Party - Sub-allocated assets [Member] - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Sub-allocation Assets	$ 168,808	$ 127,550
Percentage of Sub-allocation Assets	100.00%	100.00%
Core Sub-allocation Assets [Member]
Related Party Transaction [Line Items]
Sub-allocation Assets	$ 48,409	$ 32,474
Percentage of Sub-allocation Assets	28.70%	25.50%
Core Plus [Member]
Related Party Transaction [Line Items]
Sub-allocation Assets	$ 39,543	$ 30,155
Percentage of Sub-allocation Assets	23.40%	23.60%
Yield [Member]
Related Party Transaction [Line Items]
Sub-allocation Assets	$ 58,791	$ 48,557
Percentage of Sub-allocation Assets	34.80%	38.00%
High Alpha [Member]
Related Party Transaction [Line Items]
Sub-allocation Assets	$ 6,776	$ 5,062
Percentage of Sub-allocation Assets	4.00%	4.00%
Other Sub-allocation Assets [Member]
Related Party Transaction [Line Items]
Sub-allocation Assets	$ 15,289	$ 11,302
Percentage of Sub-allocation Assets	9.10%	8.90%