Reportable Business Segments, Reconciliation of Segment Operating Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation of segment operating income to consolidated income before income taxes
Segment operating income	$ 444.2	$ 377.9	$ 1,229.3	$ 1,028.2
Interest expense	(24.8)	(24.6)	(75.3)	(67.3)
Other income, net	0.2	5.1	2.5	12.9
Stock-based compensation expense	(14.4)	(12.6)	(40.4)	(37.1)
Acquisition-related expenses				(4.0)
Other operating expenses	(13.9)	(12.1)	(39.6)	(35.5)
Income before income taxes	419.6	358.4	1,156.5	973.8
Operating Segment
Reconciliation of segment operating income to consolidated income before income taxes
Segment operating income	$ 472.5	$ 402.6	$ 1,309.3	$ 1,104.8

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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