Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		Dec. 28, 2018	Dec. 29, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		$ 0.0	$ 205.7
Business Combination, Contingent Consideration, Liability	[1]	5.6	14.2
Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0.0	205.7
Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	[1]	5.6	14.2
Deferred Compensation Plan Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets	[2]	28.5	27.1
Deferred Compensation Plan Assets [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets	[2]	28.5	27.1
Derivative Financial Instruments, Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	[3]	0.4	0.5
Derivative Financial Instruments, Assets [Member] | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	[3]	0.4	0.5
Deferred Compensation Plan Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	[2]	28.5	27.1
Deferred Compensation Plan Liabilities [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	[2]	28.5	27.1
Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	[3]	0.0	0.1
Derivative Liabilities [Member] | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	[3]	0.0	0.1
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[4]	0.0	9.6
US Treasury Securities [Member] | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[4]	0.0	9.6
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[4]	0.0	96.0
Corporate Debt Securities [Member] | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[4]	0.0	96.0
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[4]	0.0	100.1
Commercial Paper [Member] | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[4]	0.0	100.1
Other Current and Non Current Liabilities [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		59.1
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets		28.9	233.3
Financial Liabilities Fair Value Disclosure		34.1	41.4
Fair Value, Measurements, Recurring [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets		28.5	27.1
Financial Liabilities Fair Value Disclosure		28.5	27.1
Fair Value, Measurements, Recurring [Member] | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets		0.4	206.2
Financial Liabilities Fair Value Disclosure		0.0	0.1
Fair Value, Measurements, Recurring [Member] | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets			0.0
Financial Liabilities Fair Value Disclosure		$ 5.6	$ 14.2

[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.

[2] The Company maintains a self-directed, non-qualified deferred compensation plan for certain executives and other highly compensated employees. The plan assets and liabilities are invested in actively traded mutual funds and individual stocks valued using observable quoted prices in active markets. Deferred compensation plan assets and liabilities are included in Other non-current assets and Other non-current liabilities, respectively, on the Company's Consolidated Balance Sheets.

[3] Derivative assets and liabilities primarily represent forward currency exchange contracts. The Company typically enters into these contracts to minimize the short-term impact of foreign currency exchange rates on certain trade and inter-company receivables and payables. Derivative assets and liabilities are included in Other current assets and Other current liabilities on the Company's Consolidated Balance Sheets.

[4] The Company’s available-for sale securities are valued using readily available pricing sources for comparable instruments, or model-driven valuations using significant inputs derived from or corroborated by observable market data, including yield curves and credit ratings.