Reportable Business Segments, Reconciliation of Segment Operating Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reconciliation of segment operating income to consolidated income before income taxes
Segment operating income	$ 408.2	$ 336.2	$ 785.1	$ 650.3
Interest expense	(26.0)	(23.4)	(50.5)	(42.7)
Other income, net	0.1	4.4	2.4	7.9
Stock-based compensation expense	(13.3)	(12.3)	(26.0)	(24.4)
Acquisition-related expenses		(4.0)		(4.0)
Other operating expenses	(12.9)	(11.9)	(25.8)	(23.4)
Income before income taxes	382.3	317.2	737.0	615.5
Operating Segment
Reconciliation of segment operating income to consolidated income before income taxes
Segment operating income	$ 434.4	$ 364.4	$ 836.9	$ 702.1