Comprehensive Income (Changes in AOCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	$ (195.1)	$ (204.7)
Other comprehensive income (loss) before reclassifications	41.9	(2.5)
Amounts reclassified from AOCI	(4.2)	12.1
Net other comprehensive income (loss)	37.7	9.6
Ending balance	(157.4)	(195.1)
Gains (Losses) on Cash Flow Hedges [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	5.6	(8.4)
Other comprehensive income (loss) before reclassifications	10.5	6.0
Amounts reclassified from AOCI	(8.7)	8.0
Net other comprehensive income (loss)	1.8	14.0
Ending balance	7.4	5.6
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	2.3	4.4
Other comprehensive income (loss) before reclassifications	(0.5)	(2.1)
Amounts reclassified from AOCI	0.0	0.0
Net other comprehensive income (loss)	(0.5)	(2.1)
Ending balance	1.8	2.3
Defined Benefit Plan Items [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	(130.0)	(139.3)
Other comprehensive income (loss) before reclassifications	(2.0)	5.2
Amounts reclassified from AOCI	4.5	4.1
Net other comprehensive income (loss)	2.5	9.3
Ending balance	(127.5)	(130.0)
Foreign Currency Translation Adjustments [Member]
Changes in AOCI by component (net of tax) [Roll Forward]
Beginning balance	(73.0)	(61.4)
Other comprehensive income (loss) before reclassifications	33.9	(11.6)
Amounts reclassified from AOCI	0.0	0.0
Net other comprehensive income (loss)	33.9	(11.6)
Ending balance	$ (39.1)	$ (73.0)