Comprehensive Income (Changes in AOCL) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Changes in AOCI by component (net of tax) [Roll Forward]
Balance as of beginning of period			$ (157.4)
Other comprehensive loss before reclassifications			(45.8)
Amounts reclassified from AOCL			27.6
Net other comprehensive (loss) income			(18.2)
Balance as of end of period	$ (175.6)		(175.6)
Gains (Losses) on Cash Flow Hedges [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Balance as of beginning of period			7.4
Other comprehensive loss before reclassifications			(5.6)
Amounts reclassified from AOCL			(5.6)
Net other comprehensive (loss) income			(11.2)
Balance as of end of period	(3.8)		(3.8)
Unrealized Gains on Available-for-Sale Securities [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Balance as of beginning of period			1.8
Other comprehensive loss before reclassifications			(1.8)
Amounts reclassified from AOCL			0.0
Net other comprehensive (loss) income			(1.8)
Balance as of end of period	0.0		0.0
Defined Benefit Pension Plan Items [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Balance as of beginning of period			(127.5)
Other comprehensive loss before reclassifications			(29.0)
Amounts reclassified from AOCL			5.3
Net other comprehensive (loss) income			(23.7)
Balance as of end of period	(151.2)		(151.2)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Balance as of beginning of period			(39.1)
Other comprehensive loss before reclassifications			(9.4)
Amounts reclassified from AOCL	(5.0)	$ 0.0	27.9	$ 0.0
Net other comprehensive (loss) income			18.5
Balance as of end of period	$ (20.6)		$ (20.6)