Business Segments - Amortization of Deferred Policy Acquisition Costs By Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Amortization of deferred policy acquisition costs	$ 641.8	$ 408.3	$ 377.1