Accumulated Other Comprehensive Income (Loss) - Amounts in OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	$ (183.5)	$ (74.9)	$ (68.0)
Amounts Arising During the Current Period, Income Tax	8.6	19.5	16.7
Amounts Reclassified to Net Income (Loss), Pretax	172.0	54.3	53.1
Amounts Reclassified to Net Income (Loss), income Tax	(13.6)	(17.7)	(17.6)
Other comprehensive loss	(16.5)	(18.8)	(15.8)
Cost of revenues	2,703.3	2,608.2	2,391.7
Selling, general and administrative expenses	509.2	468.2	424.3
Interest and other income (expense)	(38.8)	(60.2)	(39.1)
Other operating income (expense)	(1.7)	3.3	(20.1)
Benefit plan adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(31.4)	(99.3)	(39.5)
Amounts Arising During the Current Period, Income Tax	8.6	21.2	16.7
Amounts Reclassified to Net Income (Loss), Pretax	65.0	54.9	51.3
Amounts Reclassified to Net Income (Loss), income Tax	(13.3)	(18.2)	(17.6)
Other comprehensive loss	28.9	(41.4)	10.9
Foreign currency translation adjustments(b)
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(151.6)	22.7	(26.6)
Amounts Arising During the Current Period, Income Tax	0.0	(1.0)	0.2
Amounts Reclassified to Net Income (Loss), Pretax	107.2	0.0	(0.1)
Amounts Reclassified to Net Income (Loss), income Tax	(0.3)	0.0	0.0
Other comprehensive loss	(44.7)	21.7	(26.5)
Unrealized gains (losses) on available-for-sale securities
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax		1.7	0.4
Amounts Arising During the Current Period, Income Tax		(0.6)	(0.2)
Amounts Reclassified to Net Income (Loss), Pretax		(1.5)	(0.5)
Amounts Reclassified to Net Income (Loss), income Tax		0.5	0.2
Other comprehensive loss	0.0	0.1	(0.1)
Gains (losses) on cash flow hedges
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	0.3	(0.1)	(1.2)
Amounts Arising During the Current Period, Income Tax	0.0	(0.1)	0.0
Amounts Reclassified to Net Income (Loss), Pretax	(0.2)	0.2	2.0
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.0	(0.2)
Other comprehensive loss	0.1	0.0	0.6
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	(0.1)	(0.3)
Other operating income (expense)	0.0	(0.1)	1.3
AOCI Attributable to Parent
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(182.7)	(75.0)	(66.9)
Amounts Arising During the Current Period, Income Tax	8.6	19.5	16.7
Amounts Reclassified to Net Income (Loss), Pretax	172.0	53.6	52.7
Amounts Reclassified to Net Income (Loss), income Tax	(13.6)	(17.7)	(17.6)
Other comprehensive loss	(15.7)	(19.6)	(15.1)
Benefit plan adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax		(0.8)	(1.5)
Amounts Arising During the Current Period, Income Tax		0.0	0.0
Amounts Reclassified to Net Income (Loss), Pretax		0.7	0.4
Amounts Reclassified to Net Income (Loss), income Tax		0.0	0.0
Other comprehensive loss		(0.1)	(1.1)
Foreign currency translation adjustments
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(0.8)	0.9	0.4
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	0.0
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.0	0.0
Other comprehensive loss	(0.8)	0.9	0.4
AOCI Attributable to Noncontrolling Interest
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(0.8)	0.1	(1.1)
Amounts Arising During the Current Period, Income Tax	0.0	0.0	0.0
Amounts Reclassified to Net Income (Loss), Pretax	0.0	0.7	0.4
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.0	0.0
Other comprehensive loss	(0.8)	0.8	(0.7)
Benefit plan adjustments(a)
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(31.4)	(100.1)	(41.0)
Amounts Arising During the Current Period, Income Tax	8.6	21.2	16.7
Amounts Reclassified to Net Income (Loss), Pretax	65.0	55.6	51.7
Amounts Reclassified to Net Income (Loss), income Tax	(13.3)	(18.2)	(17.6)
Other comprehensive loss	28.9	(41.5)	9.8
Benefit plan adjustments(a) | Reclassification out of Accumulated Other Comprehensive Income
Other Comprehensive Income Loss [Line Items]
Cost of revenues	8.4	9.0	8.9
Selling, general and administrative expenses	2.3	2.4	1.6
Interest and other income (expense)	39.7	47.8	40.3
Foreign currency translation adjustments(b)
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	(152.4)	23.6	(26.2)
Amounts Arising During the Current Period, Income Tax	0.0	(1.0)	0.2
Amounts Reclassified to Net Income (Loss), Pretax	107.2	0.0	(0.1)
Amounts Reclassified to Net Income (Loss), income Tax	(0.3)	0.0	0.0
Other comprehensive loss	(45.5)	22.6	(26.1)
Unrealized gains (losses) on available-for-sale securities(c)
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax		1.7	0.4
Amounts Arising During the Current Period, Income Tax		(0.6)	(0.2)
Amounts Reclassified to Net Income (Loss), Pretax		(1.5)	(0.5)
Amounts Reclassified to Net Income (Loss), income Tax		0.5	0.2
Other comprehensive loss		0.1	(0.1)
Gains (losses) on cash flow hedges(d)
Other Comprehensive Income Loss [Line Items]
Amounts Arising During the Current Period, Pretax	0.3	(0.1)	(1.2)
Amounts Arising During the Current Period, Income Tax	0.0	(0.1)	0.0
Amounts Reclassified to Net Income (Loss), Pretax	(0.2)	0.2	2.0
Amounts Reclassified to Net Income (Loss), income Tax	0.0	0.0	(0.2)
Other comprehensive loss	$ 0.1	$ 0.0	$ 0.6