Revenue Recognition - Schedule of Investment Product Fees (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Investment product fees	$ 145	$ 143
% Change	1.00%
Mutual Fund Service Fees [Member]
Disaggregation of Revenue [Line Items]
Investment product fees	$ 80	67
% Change	19.00%
Investment Program Fees [Member]
Disaggregation of Revenue [Line Items]
Investment product fees	$ 64	69
% Change	(7.00%)
Other [Member]
Disaggregation of Revenue [Line Items]
Investment product fees	$ 1	$ 7
% Change	(86.00%)