Quarterly Financial Information (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended												12 Months Ended
	Jan. 01, 2022	Oct. 02, 2021	Jul. 03, 2021	Apr. 03, 2021	Jan. 02, 2021	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Jan. 01, 2022	Jan. 02, 2021	Dec. 28, 2019
Interim Period, Costs Not Allocable [Line Items]
Net Sales	$ 1,216.6	$ 892.7	$ 886.9	$ 814.1	$ 780.5	$ 758.2	$ 634.1	$ 734.2					$ 3,810.3	$ 2,907.0	$ 3,238.0
Gross Profit	334.2	254.6	251.5	245.4	213.5	221.6	170.3	203.3					1,085.7	808.7	860.7
Income (Loss) from Operations	18.9	107.4	109.0	97.1	74.2	90.0	45.9	70.0					332.4	280.1	351.1
Net Income	(3.2)	71.1	81.2	67.0	51.5	66.3	29.3	46.7					216.1	193.8	242.6
Net Income Attributable to Regal Beloit Corporation	$ (4.8)	$ 69.5	$ 79.6	$ 65.6	$ 50.4	$ 65.0	$ 28.1	$ 45.8					$ 209.9	$ 189.3	$ 238.9
Basic (in dollars per share)	$ (0.07)	$ 1.71	$ 1.96	$ 1.62	$ 1.24	$ 1.60	$ 0.69	$ 1.13					$ 4.44	$ 4.66	$ 5.69
Assuming Dilution (in dollars per share)	$ (0.07)	$ 1.70	$ 1.94	$ 1.60	$ 1.23	$ 1.60	$ 0.69	$ 1.12					$ 4.40	$ 4.64	$ 5.66
Basic (in shares)	67.1	40.7	40.7	40.6	40.6	40.6	40.5	40.6					47.3	40.6	42.0
Assuming Dilution (in shares)	67.7	41.0	41.0	41.0	40.9	40.8	40.7	40.8					47.7	40.8	42.2
Commercial Systems
Interim Period, Costs Not Allocable [Line Items]
Net Sales	$ 257.1	$ 268.7	$ 269.3	$ 237.0	$ 226.4	$ 218.5	$ 175.9	$ 199.4					$ 1,032.1	$ 820.2	$ 905.3
Gross Profit						61.4	42.3	50.7	$ 48.6	$ 53.6	$ 65.2	$ 65.5			232.9
Income (Loss) from Operations	16.2	30.4	25.4	27.5	22.2	24.6	6.2	12.1
Industrial Systems
Interim Period, Costs Not Allocable [Line Items]
Net Sales	146.7	148.0	145.2	136.4	139.8	138.8	120.6	129.6					576.3	528.8	575.4
Gross Profit						31.2	24.9	22.6	$ 24.0	$ 23.7	$ 27.8	$ 23.9			99.3
Income (Loss) from Operations	(27.3)	6.4	3.1	3.7	(14.9)	7.3	3.2	(0.1)
Climate Solutions
Interim Period, Costs Not Allocable [Line Items]
Net Sales	265.8	268.4	257.3	239.1	224.5	234.0	178.2	210.1					$ 1,030.6	$ 846.8	$ 968.5
Income (Loss) from Operations	47.2	52.1	46.5	43.3	41.3	39.2	20.0	29.5
Motion Control Solutions
Interim Period, Costs Not Allocable [Line Items]
Net Sales	547.0	207.6	215.1	201.6	189.8	166.9	159.4	195.1
Income (Loss) from Operations	$ (17.2)	$ 18.5	$ 34.0	$ 22.6	$ 25.6	$ 18.9	$ 16.5	$ 28.5