Changes in Accumulated Other Comprehensive Income (Loss) by Component (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 9,706.1	$ 8,592.9
Reclassified out of AOCI	106.3	56.3	$ (62.6)
Net other comprehensive income (loss)	49.8	(1.6)	(271.7)
Ending balance	10,390.0	9,706.1	8,592.9
Derivative Contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(15.3)	2.0	1.2
Recorded into AOCI	(78.4)	(57.0)	90.9
Reclassified out of AOCI	64.5	39.7	(90.5)
Net other comprehensive income (loss)	(13.9)	(17.3)	0.4
Reclassifications to retained earnings in accordance with ASU 2018-02			0.4
Ending balance	(29.2)	(15.3)	2.0
Marketable Debt Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	6.1	(2.3)	(1.8)
Recorded into AOCI	10.3	8.7	0.1
Reclassified out of AOCI	(1.8)	(0.3)	(0.1)
Net other comprehensive income (loss)	8.5	8.4
Reclassifications to retained earnings in accordance with ASU 2018-02			(0.5)
Ending balance	14.6	6.1	(2.3)
Pension Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(517.7)	(477.8)	(375.6)
Recorded into AOCI	(104.0)	(56.8)	(86.8)
Reclassified out of AOCI	43.6	16.9	28.0
Net other comprehensive income (loss)	(60.4)	(39.9)	(58.8)
Reclassifications to retained earnings in accordance with ASU 2018-02			(43.4)
Ending balance	(578.1)	(517.7)	(477.8)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(573.2)	(620.4)	(417.4)
Recorded into AOCI	115.6	47.2	(213.3)
Net other comprehensive income (loss)	115.6	47.2	(213.3)
Reclassifications to retained earnings in accordance with ASU 2018-02			10.3
Ending balance	(457.6)	(573.2)	(620.4)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,100.1)	(1,098.5)	(793.6)
Recorded into AOCI	(56.5)	(57.9)	(209.1)
Reclassified out of AOCI	106.3	56.3	(62.6)
Net other comprehensive income (loss)	49.8	(1.6)	(271.7)
Reclassifications to retained earnings in accordance with ASU 2018-02			(33.2)
Ending balance	$ (1,050.3)	$ (1,100.1)	$ (1,098.5)