Financial Instruments (Outstanding Costless Collar Hedges) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Interest expense	$ (314.6)	$ (355.6)	$ (392.0)
Realized loss reclassified into earnings	4.6	5.8	1.0
Interest Rate Swap, Net Settlements
Derivative [Line Items]
Gain (loss) on fair value hedges recognized in earnings	7.9	5.7	1.0
Interest Rate Swap
Derivative [Line Items]
Gain (loss) on fair value hedges recognized in earnings	(5.2)	7.6	8.1
Interest Expense | Interest Rate Swap
Derivative [Line Items]
Derivative Instruments gain (loss), net	(4.4)	(0.1)	0.0
Interest Expense | Terminated interest rate locks
Derivative [Line Items]
Derivative Instruments gain (loss), net	(0.3)	(2.7)	(0.5)
Interest Expense | Fair Value Hedging | Interest Rate Swap, Net Settlements
Derivative [Line Items]
Gain (loss) on fair value hedges recognized in earnings	7.9	5.7	1.0
Interest Expense | Fair Value Hedging | Interest Rate Swap, Net Periodic Earnings
Derivative [Line Items]
Gain (loss) on fair value hedges recognized in earnings	(0.1)	2.0	0.6
Interest Expense | Fair Value Hedging | Interest Rate Swap, Effect Of Dedesignation
Derivative [Line Items]
Gain (loss) on fair value hedges recognized in earnings	0.0	4.7	0.0
Interest Expense | Cash Flow Hedging | Interest Rate Swap Locks
Derivative [Line Items]
Realized loss reclassified into earnings	$ (4.6)	$ (5.8)	$ (1.0)