Comprehensive Income (Changes in AOCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	$ (188.8)	$ (157.4)
Other comprehensive income (loss) before reclassifications	(1.1)	(61.9)
Amounts reclassified from AOCL	86.1	30.5
Net other comprehensive (loss) income	85.0	(31.4)
Ending balance	(103.8)	(188.8)
Gains (Losses) on Cash Flow Hedges [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	(6.2)	7.4
Other comprehensive income (loss) before reclassifications	0.9	(8.9)
Amounts reclassified from AOCL	5.3	(4.7)
Net other comprehensive (loss) income	6.2	(13.6)
Ending balance	0.0	(6.2)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	0.0	1.8
Other comprehensive income (loss) before reclassifications	0.0	(1.8)
Amounts reclassified from AOCL	0.0	0.0
Net other comprehensive (loss) income	0.0	(1.8)
Ending balance	0.0	0.0
Defined Benefit Plan Items [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	(154.5)	(127.5)
Other comprehensive income (loss) before reclassifications	(5.7)	(34.3)
Amounts reclassified from AOCL	78.7	7.3
Net other comprehensive (loss) income	73.0	(27.0)
Ending balance	(81.5)	(154.5)
Foreign Currency Translation Adjustments [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	(28.1)	(39.1)
Other comprehensive income (loss) before reclassifications	3.7	(16.9)
Amounts reclassified from AOCL	2.1	27.9
Net other comprehensive (loss) income	5.8	11.0
Ending balance	$ (22.3)	$ (28.1)