Segment Reporting - Additional Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) Segment	Jun. 30, 2020 USD ($)
Segment Reporting Information
Number of reportable segments | Segment			3
Operating revenues	$ 1,360.8	$ 1,032.8	$ 2,589.4	$ 2,151.9
Other
Segment Reporting Information
Operating revenues	88.5	89.8	186.9	189.2
Other | Other Insurance
Segment Reporting Information
Operating revenues	$ 12.1	$ 22.5	$ 30.2	$ 47.2