Quarterly Data - Schedule of Quarterly Data (unaudited) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Condensed Income Statements, Captions [Line Items]
Net sales									$ 4,067.7	$ 4,070.4	$ 4,000.3
Net earnings	$ 175.0	$ 169.2	$ 184.9	$ 182.1	$ 179.3	$ 167.4	$ 182.7	$ 166.8	711.2	696.2	572.2
Net earnings attributable to Snap-on Incorporated	$ 170.6	$ 164.6	$ 180.4	$ 177.9	$ 175.0	$ 163.2	$ 178.7	$ 163.0	$ 693.5	$ 679.9	$ 557.7
Earnings per share - basic (in dollars per share)	$ 3.12	$ 2.99	$ 3.27	$ 3.21	$ 3.14	$ 2.90	$ 3.17	$ 2.87	$ 12.59	$ 12.08	$ 9.72
Earnings per share - diluted (in dollars per share)	3.08	2.96	3.22	3.16	3.09	2.85	3.12	2.82	12.41	11.87	9.52
Cash dividends paid per share (in dollars per share)	$ 1.08	$ 0.95	$ 0.95	$ 0.95	$ 0.95	$ 0.82	$ 0.82	$ 0.82	$ 3.93	$ 3.41	$ 2.95
Product And Services, Excluding Financial Services
Condensed Income Statements, Captions [Line Items]
Net sales	$ 955.2	$ 901.8	$ 951.3	$ 921.7	$ 952.5	$ 898.1	$ 954.6	$ 935.5	$ 3,730.0	$ 3,740.7	$ 3,686.9
Gross profit	450.5	448.1	473.8	471.6	457.4	453.9	487.1	471.6	1,844.0	1,870.0	1,825.9
Financial services expenses									(1,886.0)	(1,870.7)	(1,861.0)
Financial Service
Condensed Income Statements, Captions [Line Items]
Net sales	83.9	84.1	84.1	85.6	82.7	82.0	82.0	83.0	337.7	329.7	313.4
Financial services expenses	$ (21.7)	$ (23.1)	$ (23.5)	$ (23.5)	$ (26.6)	$ (22.7)	$ (24.2)	$ (26.1)	$ (91.8)	$ (99.6)	$ (95.9)