Accumulated Other Comprehensive Income (Loss) - Amounts in OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	$ 47.1	$ 208.5	$ 73.3
Amounts Arising During the Current Period, Income Tax	3.8	(43.0)	(37.3)
Amounts Reclassified to Net Income (Loss), Pretax	(9.4)	48.4	71.5
Amounts Reclassified to Net Income (Loss), income Tax	0.7	(12.9)	(18.0)
Other comprehensive income	42.2	201.0	89.5
Cost of revenues	3,707.1	3,461.9	3,235.8
Selling, general and administrative expenses	688.1	687.0	629.7
Interest and other income (expense)	14.4	3.7	(7.0)
Other operating income (expense)	54.2	25.3	(20.0)
Interest expense	203.8	138.8	112.2
Benefit plan adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(17.4)	197.3	120.5
Amounts Arising During the Current Period, Income Tax	4.3	(45.4)	(28.0)
Amounts Reclassified to Net Income (Loss), Pretax	2.2	41.5	64.6
Amounts Reclassified to Net Income (Loss), income Tax	(0.6)	(10.1)	(16.3)
Other comprehensive income	(11.5)	183.3	140.8
Foreign currency translation adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	65.6	(6.5)	(52.6)
Amounts Arising During the Current Period, Income Tax	4.0	2.7	(6.8)
Amounts Reclassified to Net Income (Loss), Pretax	(5.2)	(5.8)	(4.1)
Amounts Reclassified to Net Income (Loss), income Tax	1.2	1.4	1.0
Other comprehensive income	65.6	(8.2)	(62.5)
Gains (losses) on available-for-sale securities
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(0.8)	(1.2)	(0.1)
Amounts Arising During the Current Period, Income Tax	(3.7)	0.5	0.0
Amounts Reclassified to Net Income (Loss), Pretax	5.0	0.3	0.0
Amounts Reclassified to Net Income (Loss), income Tax	(1.7)	(0.1)	0.0
Other comprehensive income	(1.2)	(0.5)	(0.1)
Gains (losses) on cash flow hedges
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	1.9	25.2	8.1
Amounts Arising During the Current Period, Income Tax	(0.8)	(0.8)	(2.5)
Amounts Reclassified to Net Income (Loss), Pretax	(11.3)	12.4	11.0
Amounts Reclassified to Net Income (Loss), income Tax	1.8	(4.1)	(2.7)
Other comprehensive income	(8.4)	32.7	13.9
Gains (losses) on cash flow hedges | Reclassification out of Accumulated Other Comprehensive Income
Other Comprehensive Income Loss [Line Items]
Other operating income (expense)	7.8	8.9	(0.1)
Interest expense	(19.1)	3.5	11.1
AOCI Attributable to Parent
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	49.3	214.8	75.9
Amounts Arising During the Current Period, Income Tax	3.8	(43.0)	(37.3)
Amounts Reclassified to Net Income (Loss), Pretax	(9.3)	48.4	71.5
Amounts Reclassified to Net Income (Loss), income Tax	0.7	(12.9)	(18.0)
Other comprehensive income	44.5	207.3	92.1
Benefit plan adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	0.0	0.4	(0.4)
Amounts Arising During the Current Period, Income Tax	0.0	0.0	0.0
Amounts Reclassified to Net Income (Loss), Pretax	(0.1)	0.0	0.0
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.0	0.0
Other comprehensive income	(0.1)	0.4	(0.4)
Foreign currency translation adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(2.2)	(6.7)	(2.2)
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	(2.2)	(6.7)	(2.2)
AOCI Attributable to Noncontrolling Interest
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(2.2)	(6.3)	(2.6)
Amounts Arising During the Current Period, Income Tax	0.0	0.0	0.0
Amounts Reclassified to Net Income (Loss), Pretax	(0.1)	0.0	0.0
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.0	0.0
Other comprehensive income	(2.3)	(6.3)	(2.6)
Benefit plan adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(17.4)	197.7	120.1
Amounts Arising During the Current Period, Income Tax	4.3	(45.4)	(28.0)
Amounts Reclassified to Net Income (Loss), Pretax	2.1	41.5	64.6
Amounts Reclassified to Net Income (Loss), income Tax	(0.6)	(10.1)	(16.3)
Other comprehensive income	(11.6)	183.7	140.4
Benefit plan adjustments | Reclassification out of Accumulated Other Comprehensive Income
Other Comprehensive Income Loss [Line Items]
Cost of revenues	5.9	6.3	7.2
Selling, general and administrative expenses	2.0	1.9	2.0
Interest and other income (expense)	0.5	16.7	38.7
Foreign currency translation adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	63.4	(13.2)	(54.8)
Amounts Arising During the Current Period, Income Tax	4.0	2.7	(6.8)
Amounts Reclassified to Net Income (Loss), Pretax	(5.2)	(5.8)	(4.1)
Amounts Reclassified to Net Income (Loss), income Tax	1.2	1.4	1.0
Other comprehensive income	63.4	(14.9)	(64.7)
Gains (losses) on available-for-sale securities
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(0.8)	(1.2)	(0.1)
Amounts Arising During the Current Period, Income Tax	(3.7)	0.5	0.0
Amounts Reclassified to Net Income (Loss), Pretax	5.0	0.3	0.0
Amounts Reclassified to Net Income (Loss), income Tax	(1.7)	(0.1)	0.0
Other comprehensive income	(1.2)	(0.5)	(0.1)
Gains (losses) on available-for-sale securities | Reclassification out of Accumulated Other Comprehensive Income
Other Comprehensive Income Loss [Line Items]
Interest and other income (expense)	(5.0)	(0.3)	0.0
Gains (losses) on cash flow hedges
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	1.9	25.2	8.1
Amounts Arising During the Current Period, Income Tax	(0.8)	(0.8)	(2.5)
Amounts Reclassified to Net Income (Loss), Pretax	(11.3)	12.4	11.0
Amounts Reclassified to Net Income (Loss), income Tax	1.8	(4.1)	(2.7)
Other comprehensive income	$ (8.4)	$ 32.7	$ 13.9