Accumulated Other Comprehensive Income (Loss) Reclassification Adjustments (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Interest expense		$ (52.5)	$ (45.2)	$ (153.3)	$ (99.6)
Investment Income, Nonoperating		1.9	2.2	7.0	7.6
Total reclassifications for the period		3.0	(1.0)	7.8	3.7
Interest Rate Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Interest expense		0.8	1.0	1.8	2.1
Net actuarial loss amortization | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net periodic benefit cost	[1]	2.2	(2.0)	6.0	1.6
Net actuarial loss amortization, tax		(0.4)	1.0	(1.2)	0.8
Pension and Other Post-retirement Benefits
Total reclassifications for the period		$ 2.2	$ (2.0)	$ 6.0	$ 1.6

[1] Pension and other post-retirement benefits AOCI components are included in the computation of net periodic benefit cost (refer to note 16).