Comprehensive (Loss) Income - Reclassifications from Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Net realized loss	$ (20.8)	$ (18.6)	$ 0.9
Reclassifications from Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassifications before tax	1.5
Income tax benefit	0.4
Reclassifications, net of tax	1.1
Reclassifications from Accumulated Other Comprehensive Loss | Interest Rate Collars: Net Realized Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Net realized loss	$ 1.5