Accumulated Other Comprehensive Income (Loss) - Amounts in OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	$ (73.0)	$ (56.9)	$ (183.5)
Amounts Arising During the Current Period, Income Tax	20.2	9.2	8.6
Amounts Reclassified to Net Income (Loss), Pretax	44.4	61.2	172.0
Amounts Reclassified to Net Income (Loss), income Tax	(7.8)	(9.6)	(13.6)
Other comprehensive income (loss)	(16.2)	3.9	(16.5)
Cost of revenues	2,877.3	2,832.1	2,703.3
Selling, general and administrative expenses	584.5	604.9	509.2
Interest and other income (expense)	(37.7)	(52.7)	(38.8)
Other operating income (expense)	(15.6)	(9.4)	(1.7)
Interest expense	96.5	90.6	66.7
Benefit plan adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(98.5)	(38.0)	(31.4)
Amounts Arising During the Current Period, Income Tax	22.7	4.4	8.6
Amounts Reclassified to Net Income (Loss), Pretax	56.7	61.4	65.0
Amounts Reclassified to Net Income (Loss), income Tax	(12.7)	(9.9)	(13.3)
Other comprehensive income (loss)	(31.8)	17.9	28.9
Foreign currency translation adjustments(b)
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	19.6	(0.9)	(151.6)
Amounts Arising During the Current Period, Income Tax	0.0	0.0	0.0
Amounts Reclassified to Net Income (Loss), Pretax	0.0	0.0	107.2
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.1	(0.3)
Other comprehensive income (loss)	19.6	(0.8)	(44.7)
Gains (losses) on cash flow hedges
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	1.1	(18.8)	0.3
Amounts Arising During the Current Period, Income Tax	(2.5)	4.8	0.0
Amounts Reclassified to Net Income (Loss), Pretax	(12.3)	(0.2)	(0.2)
Amounts Reclassified to Net Income (Loss), income Tax	4.9	0.2	0.0
Other comprehensive income (loss)	(8.8)	(14.0)	0.1
Gains (losses) on cash flow hedges | Reclassification out of Accumulated Other Comprehensive Income
Other Comprehensive Income Loss [Line Items]
Interest and other income (expense)	0.0	0.0	0.0
Other operating income (expense)	22.1	5.8	0.0
Interest expense	9.8
AOCI Attributable to Parent
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(77.8)	(57.7)	(182.7)
Amounts Arising During the Current Period, Income Tax	20.2	9.2	8.6
Amounts Reclassified to Net Income (Loss), Pretax	44.4	61.2	172.0
Amounts Reclassified to Net Income (Loss), income Tax	(7.8)	(9.6)	(13.6)
Other comprehensive income (loss)	(21.0)	3.1	(15.7)
Benefit plan adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	0.2
Other comprehensive income (loss)	0.2
Foreign currency translation adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	4.6	0.8	(0.8)
Amounts Arising During the Current Period, Income Tax	0.0	0.0	0.0
Amounts Reclassified to Net Income (Loss), Pretax	0.0	0.0	0.0
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.0	0.0
Other comprehensive income (loss)	4.6	0.8	(0.8)
AOCI Attributable to Noncontrolling Interest
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	4.8	0.8	(0.8)
Amounts Arising During the Current Period, Income Tax	0.0	0.0	0.0
Amounts Reclassified to Net Income (Loss), Pretax	0.0	0.0	0.0
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.0	0.0
Other comprehensive income (loss)	4.8	0.8	(0.8)
Benefit plan adjustments(a)
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(98.3)	(38.0)	(31.4)
Amounts Arising During the Current Period, Income Tax	22.7	4.4	8.6
Amounts Reclassified to Net Income (Loss), Pretax	56.7	61.4	65.0
Amounts Reclassified to Net Income (Loss), income Tax	(12.7)	(9.9)	(13.3)
Other comprehensive income (loss)	(31.6)	17.9	28.9
Benefit plan adjustments(a) | Reclassification out of Accumulated Other Comprehensive Income
Other Comprehensive Income Loss [Line Items]
Cost of revenues	7.7	7.8	8.4
Selling, general and administrative expenses	2.1	2.3	2.3
Interest and other income (expense)	37.9	52.7	39.7
Foreign currency translation adjustments(b)
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	24.2	(0.1)	(152.4)
Amounts Arising During the Current Period, Income Tax	0.0	0.0	0.0
Amounts Reclassified to Net Income (Loss), Pretax	0.0	0.0	107.2
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.1	(0.3)
Other comprehensive income (loss)	24.2	0.0	(45.5)
Gains (losses) on cash flow hedges(c)
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	1.1	(18.8)	0.3
Amounts Arising During the Current Period, Income Tax	(2.5)	4.8	0.0
Amounts Reclassified to Net Income (Loss), Pretax	(12.3)	(0.2)	(0.2)
Amounts Reclassified to Net Income (Loss), income Tax	4.9	0.2	0.0
Other comprehensive income (loss)	$ (8.8)	$ (14.0)	$ 0.1