Accumulated Other Comprehensive Income (Loss) - Reclasses Out Of AOCI (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016		Mar. 31, 2018
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		$ 338.2	$ 354.8	$ 330.6
Other comprehensive loss		(16.5)	(18.8)	(15.8)
Cumulative effect of change in accounting principle				0.2	[1]	$ 2.2	[2]
Acquisitions of noncontrolling interests		(21.0)
Ending Balance		166.6	338.2	354.8
Benefit plan adjustments
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		(601.0)	(559.6)	(570.5)
Other comprehensive income (loss) before reclassifications		(22.8)	(78.1)	(22.8)
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		51.7	36.7	33.7
Other comprehensive loss		28.9	(41.4)	10.9
Acquisitions of noncontrolling interests		0.0
Ending Balance		(572.1)	(601.0)	(559.6)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		(327.4)	(349.1)	(322.6)
Other comprehensive income (loss) before reclassifications		(151.6)	21.7	(26.4)
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		106.9	0.0	(0.1)
Other comprehensive loss		(44.7)	21.7	(26.5)
Acquisitions of noncontrolling interests		(9.9)
Ending Balance		(382.0)	(327.4)	(349.1)
Unrealized Gains (Losses) on Available-for-Sale Securities
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		1.1	1.0	1.1
Other comprehensive income (loss) before reclassifications		0.0	1.1	0.2
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		0.0	(1.0)	(0.3)
Other comprehensive loss		0.0	0.1	(0.1)
Acquisitions of noncontrolling interests		0.0
Ending Balance		0.0	1.1	1.0
Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		0.7	0.7	0.1
Other comprehensive income (loss) before reclassifications		0.3	(0.2)	(1.2)
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		(0.2)	0.2	1.8
Other comprehensive loss		0.1	0.0	0.6
Acquisitions of noncontrolling interests		0.0
Ending Balance		0.8	0.7	0.7
AOCI Attributable to Parent
Accumulated Other Comprehensive Income [Abstract]
Beginning Balance		(926.6)	(907.0)	(891.9)
Other comprehensive income (loss) before reclassifications		(174.1)	(55.5)	(50.2)
Amounts reclassified from accumulated other comprehensive loss to net income (loss)		158.4	35.9	35.1
Other comprehensive loss		(15.7)	(19.6)	(15.1)
Cumulative effect of change in accounting principle	[2]					(1.1)
Acquisitions of noncontrolling interests		(9.9)
Ending Balance		$ (953.3)	$ (926.6)	$ (907.0)
Accounting Standards Update 2016-01 | Unrealized Gains (Losses) on Available-for-Sale Securities
Accumulated Other Comprehensive Income [Abstract]
Cumulative effect of change in accounting principle						(1.1)
Accounting Standards Update 2016-01 | AOCI Attributable to Parent
Accumulated Other Comprehensive Income [Abstract]
Cumulative effect of change in accounting principle						$ (1.1)

[1] We elected to early adopt the provisions of ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, in the fourth quarter of 2016 resulting in a cumulative effect adjustment to Retained Earnings for previously unrecognized excess tax benefits. See Note 1 for further discussion of the impacts of this standard.

[2] Effective January 1, 2018, we adopted the provisions of ASU 2014-09, Revenue From Contracts with Customers, ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, and ASU 2016-16, Intra-Entity Transfers of Assets Other Than Inventory. We recognized a cumulative effect adjustment to January 1, 2018 retained earnings as a result of adopting each of these standards. See Note 1 for further details of the impact of each standard.