Fair Value - Gross Transfers Into (Out Of) Level 3 (Details) - Recurring - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net transfers out of Level 3	$ 1.0	$ (4.0)
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross transfers into Level 3	1.0	0.0
Gross transfers out of Level 3	0.0	(4.0)
Net transfers out of Level 3	$ 1.0	$ (4.0)