Derivative Financial Instruments - Schedule of Notional Amounts (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative, notional amount	$ 16,925.4	$ 15,841.3
Swaps
Derivative [Line Items]
Derivative, notional amount	684.5	599.5
Futures, forwards and spot
Derivative [Line Items]
Derivative, notional amount	5,467.8	3,017.1
Written options
Derivative [Line Items]
Derivative, notional amount	5,578.1	6,393.9
Purchased options
Derivative [Line Items]
Derivative, notional amount	$ 5,195.0	$ 5,830.8