Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 28, 2018	Dec. 29, 2017	Dec. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Net rent expense under operating leases		$ 42.1	$ 35.5	$ 34.4
Unconditional purchase obligations		269.0
Business Combination, Contingent Consideration, Liability	[1]	5.6	$ 14.2
Business Combination, Contingent Consideration, Liability, Current		0.1
Business Combination, Contingent Consideration, Liability, Noncurrent		$ 5.5

[1] Contingent consideration liabilities represent arrangements to pay the former owners of certain companies that Trimble acquired. The undiscounted maximum payment under the arrangements is $59.1 million at the end of fiscal 2018. The fair values are estimated using scenario-based methods or option pricing methods based upon estimated future revenues, gross margins or other milestones. Contingent consideration liabilities are included in Other current liabilities and Other non-current liabilities on the Company's Consolidated Balance Sheets.