Changes in Accumulated Other Comprehensive Income (Loss) by Component (Reclassifications) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (314.6)	$ (355.6)	$ (392.0)
Tax expense (benefit)	282.8	173.1	222.0
Net income	1,292.3	969.6	1,073.8
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(3.6)	(5.8)	(1.0)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Gain (loss) on cash flow hedges | Pension Plan
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Income	1.3	0.0	0.0
Tax expense (benefit)	0.3	0.0	0.0
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Gain (loss) on cash flow hedges | Terminated interest rate locks
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	(6.2)	(7.9)	(1.4)
Tax expense (benefit)	(1.6)	(2.1)	(0.4)
Net income		(5.8)	(1.0)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Gain (loss) on cash flow hedges | Pension Plan
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	1.0	$ 0.0	$ 0.0
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Gain (loss) on cash flow hedges | Terminated interest rate locks
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	$ (4.6)