Earnings Per Share (Schedule Of Computation Of Earnings Per Share And Effect On Weighted-Average Number Of Shares) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended			9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	[1]	Sep. 28, 2018	Sep. 29, 2017	[1]
Earnings Per Share Reconciliation [Abstract]
Net income attributable to Trimble Inc.	$ 73.7	$ 57.2		$ 196.3	$ 154.3
Weighted average number of common shares used in basic earnings per share	250.5	252.6		249.6	252.5
Effect of dilutive securities	3.1	5.3		3.4	4.5
Weighted average number of common shares and dilutive potential common shares used in diluted earnings per share	253.6	257.9		253.0	257.0
Basic earnings per share	$ 0.29	$ 0.23		$ 0.79	$ 0.61
Diluted earnings per share	$ 0.29	$ 0.22		$ 0.78	$ 0.60

[1] See Note 2 for a summary of adjustments