Segment Information (Schedule Of Revenue, Operating Income And Identifiable Assets By Segment) (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017		Sep. 28, 2018	Sep. 29, 2017
Segment Reporting Information [Line Items]
Revenues	$ 795.2	$ 676.2	[1]	$ 2,322.9	$ 1,946.7	[1]
Acquired deferred revenue adjustment	9.5	0.7	[2]	16.2	1.5	[2]
Amortization of acquired capitalized commissions	(1.8)	(0.2)	[2]	(2.9)	(0.9)	[2]
Consolidated segment operating income	77.4	66.3	[2],[3]	231.1	180.0	[2],[3]
Depreciation expense				26.2	26.4	[4]
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Consolidated segment operating income	183.6	148.9		528.9	412.6
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	804.7	676.9	[5]	2,339.1	1,948.2	[5]
Consolidated segment operating income	191.3	149.4	[2]	542.2	413.2	[2]
Depreciation expense	5.5	5.1		15.5	15.2
Buildings and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues	286.6	217.9	[1]	785.6	625.0	[1]
Acquired deferred revenue adjustment	9.2	0.1		15.1	0.4
Amortization of acquired capitalized commissions	(1.8)	(0.2)		(2.7)	(0.7)
Buildings and Infrastructure [Member] | Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Consolidated segment operating income	60.9	55.1	[1]	171.8	134.6	[1]
Buildings and Infrastructure [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	295.8	218.0	[5]	800.7	625.4	[5]
Consolidated segment operating income	68.3	55.0		184.2	134.3
Depreciation expense	1.8	1.4		4.6	4.7
Geospatial [Member]
Segment Reporting Information [Line Items]
Revenues	185.4	169.4	[1]	544.3	483.6	[1]
Acquired deferred revenue adjustment	0.0	0.0		0.0	0.0
Geospatial [Member] | Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Consolidated segment operating income	47.4	36.3	[1]	126.3	94.0	[1]
Geospatial [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	185.4	169.4	[5]	544.3	483.6	[5]
Consolidated segment operating income	47.4	36.3		126.3	94.0
Depreciation expense	1.5	1.5		4.4	4.3
Resources and Utilities [Member]
Segment Reporting Information [Line Items]
Revenues	133.0	117.2	[1]	437.2	349.0	[1]
Acquired deferred revenue adjustment	0.2	0.4		0.8	0.6
Amortization of acquired capitalized commissions				(0.2)	(0.1)
Resources and Utilities [Member] | Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Consolidated segment operating income	38.3	27.2	[1]	132.3	104.8	[1]
Resources and Utilities [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	133.2	117.6	[5]	438.0	349.6	[5]
Consolidated segment operating income	38.5	27.6		132.9	105.3
Depreciation expense	1.1	0.9		3.1	2.1
Transportation [Member]
Segment Reporting Information [Line Items]
Revenues	190.2	171.7	[1]	555.8	489.1	[1]
Acquired deferred revenue adjustment	0.1	0.2		0.3	0.5
Amortization of acquired capitalized commissions		0.0			(0.1)
Transportation [Member] | Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Consolidated segment operating income	37.0	30.3	[1]	98.5	79.2	[1]
Transportation [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	190.3	171.9	[5]	556.1	489.6	[5]
Consolidated segment operating income	37.1	30.5		98.8	79.6
Depreciation expense	$ 1.1	$ 1.3		$ 3.4	$ 4.1

[1] See Note 2 for a summary of adjustments

[2] See Note 2 for a summary of adjustments

[3] See Note 2 for a summary of adjustments

[4] See Note 2 for a summary of adjustments

[5] Adjusted to reflect adoption of the new revenue recognition standard, Revenue from Contracts with Customers. For further information, see Note 2.