Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 29, 2017	Dec. 30, 2016	Jan. 01, 2016
Commitments and Contingencies Disclosure [Abstract]
Net rent expense under operating leases		$ 35.5	$ 34.4	$ 34.0
Unconditional purchase obligations		198.1
Business Combination, Contingent Consideration, Liability	[1]	14.2	$ 4.5
Business Combination, Contingent Consideration, Liability, Current		0.9
Business Combination, Contingent Consideration, Liability, Noncurrent		$ 13.3

[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 $50.3 million at the end of fiscal 2017.