Business Segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net revenues:	$ 1,366.1	$ 1,354.5	$ 4,021.8	$ 3,972.0
Percent change in net revenues	0.90%		1.30%
Gross profit:	$ 875.9	873.6	$ 2,576.4	2,534.2
Percent change in gross profit	0.30%		1.70%
Operating profit	$ 413.9	430.1	$ 1,191.4	1,230.1
Percent change in operating profit	(3.80%)		(3.10%)
Long-lived assets:	$ 217.3	198.5	$ 217.3	198.5
Percent change in long-lived assets	9.50%
Corporate
Segment Reporting Information [Line Items]
Unallocated corporate general and administrative expenses	$ 46.3	44.9	141.0	130.1
Application Software
Segment Reporting Information [Line Items]
Net revenues:	$ 447.9	405.4	$ 1,251.4	1,177.2
Percent change in net revenues	10.50%		6.30%
Gross profit:	$ 307.6	275.4	$ 851.8	791.5
Percent change in gross profit	11.70%		7.60%
Operating profit	$ 125.6	110.1	$ 336.6	299.9
Percent change in operating profit	14.10%		12.20%
Long-lived assets:	$ 114.1	85.6	$ 114.1	85.6
Percent change in long-lived assets	33.30%
Network Software & Systems
Segment Reporting Information [Line Items]
Net revenues:	$ 430.2	391.2	$ 1,290.4	1,103.7
Percent change in net revenues	10.00%		16.90%
Gross profit:	$ 287.1	271.9	$ 865.1	763.6
Percent change in gross profit	5.60%		13.30%
Operating profit	$ 134.3	137.5	$ 403.6	392.0
Percent change in operating profit	(2.30%)		3.00%
Long-lived assets:	$ 46.0	50.0	$ 46.0	50.0
Percent change in long-lived assets	(8.00%)
Measurement & Analytical Solutions
Segment Reporting Information [Line Items]
Net revenues:	$ 367.9	398.3	$ 1,097.0	1,208.5
Percent change in net revenues	(7.60%)		(9.20%)
Gross profit:	$ 218.4	234.7	$ 654.5	706.1
Percent change in gross profit	(6.90%)		(7.30%)
Operating profit	$ 122.5	127.0	$ 359.5	375.4
Percent change in operating profit	(3.50%)		(4.20%)
Long-lived assets:	$ 37.1	41.6	$ 37.1	41.6
Percent change in long-lived assets	(10.80%)
Process Technologies
Segment Reporting Information [Line Items]
Net revenues:	$ 120.1	159.6	$ 383.0	482.6
Percent change in net revenues	(24.70%)		(20.60%)
Gross profit:	$ 62.8	91.6	$ 205.0	273.0
Percent change in gross profit	(31.40%)		(24.90%)
Operating profit	$ 31.5	55.5	$ 91.7	162.8
Percent change in operating profit	(43.20%)		(43.70%)
Long-lived assets:	$ 20.1	$ 21.3	$ 20.1	$ 21.3
Percent change in long-lived assets	(5.60%)