Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions		Sep. 26, 2014	Sep. 29, 2017	Dec. 30, 2016	Mar. 18, 2015
Loss Contingencies [Line Items]
Unconditional purchase obligations			$ 192.6
Business Combination, Contingent Consideration, Liability	[1]		$ 17.2	$ 4.5
Pending Litigation [Member] | Recreational Data Services Plaintiff [Member]
Loss Contingencies [Line Items]
Loss Contingency, Damages Awarded, Value		$ 51.3
Final Judgment In Favor of Company					$ 0.6

[1] Contingent consideration liabilities represent arrangements to pay the former owners of certain companies that Trimble acquired. The undiscounted maximum payments under the arrangements is $60.1 million at the end of the third quarter of fiscal 2017. 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 Condensed Consolidated Balance Sheets.