Fair Value Measurements (Assets And Liabilities Measured At Fair Value On Recurring Basis) (Detail) - USD ($) $ in Millions		Jun. 29, 2018	Dec. 29, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities, Fair Value		$ 0.0	$ 205.7
Total Assets Measured at Fair Value, Recurring		31.7	233.3
Contingent Consideration, Liability	[1]	5.4	14.2
Total Liabilities Measured at Fair Value, Recurring		36.4	41.4
Other Current and Non Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High		52.5
Deferred Compensation Plan Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	[2]	30.8	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]	0.9	0.5
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets Measured at Fair Value, Recurring		30.8	27.1
Total Liabilities Measured at Fair Value, Recurring		30.8	27.1
Fair Value, Inputs, Level 1 [Member] | Deferred Compensation Plan Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	[2]	30.8	27.1
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities, Fair Value		0.0	205.7
Total Assets Measured at Fair Value, Recurring		0.9	206.2
Total Liabilities Measured at Fair Value, Recurring		0.2	0.1
Fair Value, Inputs, Level 2 [Member] | 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]	0.9	0.5
Fair Value Inputs, Level III [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets Measured at Fair Value, Recurring		0.0	0.0
Contingent Consideration, Liability	[1]	5.4	14.2
Total Liabilities Measured at Fair Value, Recurring		5.4	14.2
Deferred Compensation Plan Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan liabilities	[2]	30.8	27.1
Deferred Compensation Plan Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan liabilities	[2]	30.8	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]	0.2	0.1
Derivative Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	[3]	0.2	0.1
US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities, Fair Value	[4]	0.0	9.6
US Treasury Securities | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities, Fair Value	[4]	0.0	9.6
Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities, Fair Value	[4]	0.0	96.0
Corporate Debt Securities | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities, Fair Value	[4]	0.0	96.0
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities, Fair Value	[4]	0.0	100.1
Commercial Paper | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities, Fair Value	[4]	$ 0.0	$ 100.1

[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 $52.5 million at the end of the second quarter 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 Condensed 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 Condensed 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 Condensed 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.