Derivative Financial Instruments - Schedule of Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets, fair value gross	$ 114.9	$ 109.5
Cash collateral	6.1	9.6
Total fair value of gross derivative assets	108.8	99.9
Derivative liabilities, fair value, gross	103.8	112.9
Cash collateral	25.6	73.1
Total fair value of gross derivative liabilities	78.2	39.8
Derivative assets	72.1	68.8
Total net derivative assets	66.0	59.2
Derivative liabilities	60.9	72.1
Total net derivative liabilities	$ 35.3	$ (1.0)