Accumulated Other Comprehensive Income/(Loss) (Summary of Changes in Accumulated Other Comprehensive Income/(Loss)) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 28,948.0
Other comprehensive income before reclassifications	2,476.0
Amounts reclassified from AOCI	(9.3)
Net current period other comprehensive income/(loss)	2,466.7
Ending balance	32,654.6
Accumulated other comprehensive (loss)/income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,497.6)	$ (183.8)
Net current period other comprehensive income/(loss)	2,466.7	49.6
Ending balance	969.1	(134.2)
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,505.4)	(182.1)
Other comprehensive income before reclassifications	2,441.1
Amounts reclassified from AOCI	0.0
Net current period other comprehensive income/(loss)	2,441.1	38.8
Ending balance	935.7	(143.3)
Pension and other employee benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(5.2)	0.0
Other comprehensive income before reclassifications	9.7
Amounts reclassified from AOCI	1.3
Net current period other comprehensive income/(loss)	11.0	0.0
Ending balance	5.8	0.0
Unrealized holding gain/(loss) on available-for-sale securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	6.6	(1.7)
Other comprehensive income before reclassifications	24.7
Amounts reclassified from AOCI	(4.4)
Net current period other comprehensive income/(loss)	20.3	10.4
Ending balance	26.9	8.7
Hedging activities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	6.4	0.0
Other comprehensive income before reclassifications	0.5
Amounts reclassified from AOCI	(6.2)
Net current period other comprehensive income/(loss)	(5.7)	0.4
Ending balance	$ 0.7	$ 0.4