Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (1,282.5)	$ (1,270.8)	$ (1,299.6)	$ (1,326.5)
Other comprehensive income before reclassifications			4.2
Amounts reclassified from accumulated other comprehensive income	34.8	38.6	69.7	77.3
Current period other comprehensive income			73.9
Ending balance	(1,213.7)	(1,244.1)	(1,213.7)	(1,244.1)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,048.4)	(3,783.1)	(4,084.8)	(3,815.8)
Ending balance	(4,010.9)	$ (3,765.2)	(4,010.9)	$ (3,765.2)
Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(896.7)
Other comprehensive income before reclassifications			(44.4)
Amounts reclassified from accumulated other comprehensive income			0.0
Current period other comprehensive income			(44.4)
Ending balance	(941.1)		(941.1)
Postretirement Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(3,188.1)
Other comprehensive income before reclassifications			48.6
Amounts reclassified from accumulated other comprehensive income			69.7
Current period other comprehensive income			118.3
Ending balance	$ (3,069.8)		$ (3,069.8)