Long-Term Debt - Senior Unsecured Notes Repurchases (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Debt Disclosure [Abstract]
Debt repurchased	$ 57.2	$ 67.7
Aggregate payments	(30.8)	(36.0)
Net discount on repurchased debt	(0.3)	(0.3)
Accrued interest on repurchased debt	0.6	0.6
Gain on extinguishment of debt	$ 26.7	$ 32.0