Revenue (Disaggregation of Revenue by Geographical Area) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 6,114.0	$ 5,476.6	$ 5,636.7	$ 5,092.2	$ 5,637.6	$ 5,306.9	$ 5,585.0	$ 4,963.8	$ 22,319.5	$ 21,493.3	$ 19,973.8
U.S.
Disaggregation of Revenue [Line Items]
Revenue									12,722.6	12,391.9	11,414.4
Europe
Disaggregation of Revenue [Line Items]
Revenue									3,765.0	3,663.1	3,390.6
Japan
Disaggregation of Revenue [Line Items]
Revenue									2,547.6	2,407.4	2,339.5
Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									$ 3,284.3	$ 3,030.9	$ 2,829.3