Revenue - Market Fee Waivers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue, Major Customer [Line Items]
Reduction in investment management and service and distribution fees, gross	$ (1,721.4)	$ (1,419.0)	$ (3,381.1)	$ (3,017.9)
Investment management and Services and distribution fees
Revenue, Major Customer [Line Items]
Reduction in investment management and service and distribution fees, gross	$ 41.4	$ 8.7	$ 70.4	$ 10.7