Accumulated Other Comprehensive Income (Loss) - Reclasses Out Of AOCI (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		$ 207.6		$ 166.6	$ 338.2
Other comprehensive income (loss)		(16.2)		3.9	(16.5)
Acquisitions of noncontrolling interests					(21.0)
Ending Balance		202.5		207.6	166.6
Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		(1.7)	[1]		2.2
Ending Balance	[1]			(1.7)
Benefit plan adjustments
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		(583.0)		(572.1)	(601.0)
Other comprehensive income (loss) before reclassifications		(75.8)		(33.6)	(22.8)
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		44.0		51.5	51.7
Other comprehensive income (loss)		(31.8)		17.9	28.9
Ending Balance		(614.8)		(583.0)	(572.1)
Benefit plan adjustments | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		(28.8)
Ending Balance				(28.8)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		(382.8)		(382.0)	(327.4)
Other comprehensive income (loss) before reclassifications		19.6		(0.9)	(151.6)
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		0.0		0.1	106.9
Other comprehensive income (loss)		19.6		(0.8)	(44.7)
Acquisitions of noncontrolling interests					(9.9)
Ending Balance		(363.2)		(382.8)	(382.0)
Unrealized Gains (Losses) on Available-for-Sale Securities
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		0.0		0.0	1.1
Other comprehensive income (loss) before reclassifications		0.0		0.0	0.0
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		0.0		0.0	0.0
Other comprehensive income (loss)		0.0		0.0	0.0
Ending Balance		0.0		0.0	0.0
Unrealized Gains (Losses) on Available-for-Sale Securities | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance					(1.1)
Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		(13.2)		0.8	0.7
Other comprehensive income (loss) before reclassifications		(1.4)		(14.0)	0.3
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		(7.4)		0.0	(0.2)
Other comprehensive income (loss)		(8.8)		(14.0)	0.1
Ending Balance		(22.0)		(13.2)	0.8
AOCI Attributable to Parent
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		(979.0)		(953.3)	(926.6)
Other comprehensive income (loss) before reclassifications		(57.6)		(48.5)	(174.1)
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		36.6		51.6	158.4
Other comprehensive income (loss)		(21.0)		3.1	(15.7)
Acquisitions of noncontrolling interests					(9.9)
Ending Balance		(1,000.0)		(979.0)	(953.3)
AOCI Attributable to Parent | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		$ (28.8)			$ (1.1)
Ending Balance				$ (28.8)

[1] Effective January 1, 2019, we adopted the provisions of ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. We recognized a cumulative effect adjustment to January 1, 2019 retained earnings as a result of adopting this standard. See Note 1 for further details.(c)Effective January 1, 2020, we adopted the provisions of ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. We recognized a cumulative effect adjustment to January 1, 2020 retained earnings as a result of adopting this standard. See Note 1 for further details.