Comprehensive Income (Loss) - Reclassifications from Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income Loss [Line Items]
Net realized loss	$ (5.1)	$ (5.6)	$ (15.8)	$ (15.0)
Reclassifications from Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassifications before tax	0.6	0.6	1.7	1.0
Income tax benefit	0.2	0.2	0.5	0.3
Reclassifications, net of tax	0.4	0.4	1.2	0.7
Reclassifications from Accumulated Other Comprehensive Loss | Change in Fair Value of Interest Rate Collars
Accumulated Other Comprehensive Income Loss [Line Items]
Net realized loss	$ 0.6	$ 0.6	$ 1.7	$ 1.0