Quarterly Financial Information (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	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. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Interim Period, Costs Not Allocable [Line Items]
Net Sales	$ 780.5	$ 758.2	$ 634.1	$ 734.2	$ 738.2	$ 772.3	$ 873.7	$ 853.8	$ 2,907.0	$ 3,238.0	$ 3,645.6
Gross Profit	213.5	221.6	170.3	203.3	190.2	201.9	234.0	234.6	808.7	860.7	964.6
Income (Loss) from Operations	74.2	90.0	45.9	70.0	61.7	72.8	96.0	120.6	280.1	351.1	347.0
Net Income	51.5	66.3	29.3	46.7	37.6	50.8	67.4	86.8	193.8	242.6	235.8
Net Income Attributable to Regal Beloit Corporation	$ 50.4	$ 65.0	$ 28.1	$ 45.8	$ 36.7	$ 49.7	$ 66.6	$ 85.9	$ 189.3	$ 238.9	$ 231.2
Basic (in dollars per share)	$ 1.24	$ 1.60	$ 0.69	$ 1.13	$ 0.90	$ 1.20	$ 1.56	$ 2.01	$ 4.66	$ 5.69	$ 5.30
Assuming Dilution (in dollars per share)	$ 1.23	$ 1.60	$ 0.69	$ 1.12	$ 0.89	$ 1.19	$ 1.55	$ 1.99	$ 4.64	$ 5.66	$ 5.26
Basic (in shares)	40.6	40.6	40.5	40.6	40.9	41.5	42.6	42.8	40.6	42.0	43.6
Assuming Dilution (in shares)	40.9	40.8	40.7	40.8	41.1	41.7	43.0	43.1	40.8	42.2	43.9
Gain on Sale of Businesses								$ 41.2	$ 0.1	$ 44.7	$ 0.0
Commercial Systems
Interim Period, Costs Not Allocable [Line Items]
Net Sales	$ 226.4	$ 218.5	$ 175.9	$ 199.4	$ 202.0	$ 214.8	$ 246.3	242.2	820.2	905.3	1,110.9
Gross Profit		61.4	42.3	50.7	48.6	53.6	65.2	65.5		232.9
Income (Loss) from Operations	22.2	24.6	6.2	12.1	10.9	16.9	19.6	59.4		106.8
Industrial Systems
Interim Period, Costs Not Allocable [Line Items]
Net Sales	139.8	138.8	120.6	129.6	138.0	143.8	155.5	138.1	528.8	575.4	671.1
Gross Profit		31.2	24.9	22.6	24.0	23.7	27.8	23.9		99.3
Income (Loss) from Operations	(14.9)	7.3	3.2	(0.1)	(4.4)	(2.6)	(0.1)	(5.9)		(13.0)
Climate Solutions
Interim Period, Costs Not Allocable [Line Items]
Net Sales	224.5	234.0	178.2	210.1	206.4	230.9	267.9	263.3	846.8	968.5	1,024.8
Income (Loss) from Operations	41.3	39.2	20.0	29.5	35.7	37.6	51.7	38.9
Power Transmission Solutions
Interim Period, Costs Not Allocable [Line Items]
Net Sales	189.8	166.9	159.4	195.1	191.8	182.8	204.0	210.2	$ 711.2	$ 788.8	$ 838.8
Income (Loss) from Operations	$ 25.6	$ 18.9	$ 16.5	$ 28.5	$ 19.5	$ 20.9	$ 24.8	$ 28.2