Total Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity					$ 2,085.4		$ 2,085.4
Net income	$ 110.6		$ 108.6				286.3	$ 273.4
Other comprehensive (loss) income	(10.9)		$ (4.4)				(3.9)	$ (23.4)
Accounting Standards Update [Extensible List]									Accounting Standards Update 2016-13 [Member]
Ending equity	$ 2,178.1						$ 2,178.1
Cash dividends declared (USD per share)	$ 0.98	$ 0.98	$ 0.91	$ 0.91			$ 2.94	$ 2.73
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	$ 0.6		$ 0.6		0.6	$ 0.6	$ 0.6	$ 0.6
Ending equity	0.6	$ 0.6	0.6	$ 0.6	0.6	0.6	0.6	0.6	$ 0.6
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	0.0		2.8		4.9	0.0	4.9	0.0
Stock-based compensation	3.1		4.1		13.4	15.9
Acquisition/surrender of common shares	(3.4)		(0.6)		(18.5)	(12.0)
Directors deferred compensation	0.3		0.2		0.2	(1.1)
Ending equity	0.0	0.0	6.5	2.8	0.0	2.8	0.0	6.5	0.0
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	2,447.3		2,308.4		2,393.7	2,279.4	2,393.7	2,279.4
Net income	108.5		107.1		173.5	163.2
Acquisition/surrender of common shares	(1.0)				(13.2)	(34.1)	(14.2)	(34.1)
Cash dividends declared	(53.5)		(49.5)		(106.7)	(99.1)
Ending equity	2,501.3	2,447.3	2,366.0	2,308.4	2,447.3	2,308.4	2,501.3	2,366.0	2,279.4
Retained Earnings | Cumulative effect from adoption of CECL accounting standard
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity						(1.0)		(1.0)
Ending equity									(1.0)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	(322.2)		(351.9)		(329.2)	(332.9)	(329.2)	(332.9)
Other comprehensive (loss) income	(10.9)		(4.4)		7.0	(19.0)
Ending equity	(333.1)	(322.2)	(356.3)	(351.9)	(322.2)	(351.9)	(333.1)	(356.3)	(332.9)
Total Hubbell Shareholders' Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	2,125.7		1,959.9		2,070.0	1,947.1	2,070.0	1,947.1
Net income	108.5		107.1		173.5	163.2
Other comprehensive (loss) income	(10.9)		(4.4)		7.0	(19.0)
Stock-based compensation	3.1		4.1		13.4	15.9
Acquisition/surrender of common shares	(4.4)		(0.6)		(31.7)	(46.1)
Cash dividends declared	(53.5)		(49.5)		(106.7)	(99.1)
Directors deferred compensation	0.3		0.2		0.2	(1.1)
Ending equity	2,168.8	2,125.7	2,016.8	1,959.9	2,125.7	1,959.9	2,168.8	2,016.8	1,947.1
Total Hubbell Shareholders' Equity | Cumulative effect from adoption of CECL accounting standard
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity						(1.0)		(1.0)
Ending equity									(1.0)
Non- controlling interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	15.2		13.6		15.4	13.4	15.4	13.4
Net income	2.1		1.5		2.2	1.6
Dividends to noncontrolling interest	(8.0)		(0.9)		(2.4)	(1.4)
Ending equity	$ 9.3	$ 15.2	$ 14.2	$ 13.6	$ 15.2	$ 13.6	$ 9.3	$ 14.2	$ 13.4