Total Equity- Summary of Changes in Total Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			$ 1,960.5		$ 1,960.5
Net income	$ 108.6	$ 132.6			273.4	$ 304.3
Other comprehensive (loss) income	(4.4)	$ (16.0)			(23.4)	$ (10.0)
Accounting Standards Update [Extensible List]							us-gaap:AccountingStandardsUpdate201613Member
Ending equity	$ 2,031.0				$ 2,031.0		$ 1,960.5
Cash dividends per common share (USD per share)	$ 0.91	$ 0.84	$ 0.91	$ 0.84	$ 2.73	$ 2.52
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	$ 0.6	$ 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
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	2.8	1.2	0.0	1.3	0.0	1.3	1.3
Stock-based compensation	4.1	5.2	15.9	8.3
Acquisition/surrender of common shares	(0.6)	(5.8)	(12.0)	(8.8)
Directors deferred compensation	0.2	0.1	(1.1)	0.4
Ending equity	6.5	0.7	2.8	1.2	6.5	0.7	0.0
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	2,308.4	2,143.8	2,279.4	2,064.4	2,279.4	2,064.4	2,064.4
Net income	107.1	130.7	163.2	168.3
Reclassification of stranded tax effects				30.0
Acquisition/surrender of common shares		(1.4)	(34.1)	(27.2)	(34.1)	(28.6)
Cash dividends declared	(49.5)	(45.6)	(99.1)	(91.7)
Ending equity	2,366.0	2,227.5	2,308.4	2,143.8	2,366.0	2,227.5	2,279.4
Retained Earnings | Cumulative effect from adoption of CECL accounting standard (Note1)
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	(351.9)	(309.7)	(332.9)	(285.7)	(332.9)	(285.7)	(285.7)
Other comprehensive (loss) income	(4.4)	(16.0)	(19.0)	6.0
Reclassification of stranded tax effects				(30.0)
Ending equity	(356.3)	(325.7)	(351.9)	(309.7)	(356.3)	(325.7)	(332.9)
Total Hubbell Shareholders' Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	1,959.9	1,835.9	1,947.1	1,780.6	1,947.1	1,780.6	1,780.6
Net income	107.1	130.7	163.2	168.3
Other comprehensive (loss) income	(4.4)	(16.0)	(19.0)	6.0
Stock-based compensation	4.1	5.2	15.9	8.3
Acquisition/surrender of common shares	(0.6)	(7.2)	(46.1)	(36.0)
Cash dividends declared	(49.5)	(45.6)	(99.1)	(91.7)
Directors deferred compensation	0.2	0.1	(1.1)	0.4
Ending equity	2,016.8	1,903.1	1,959.9	1,835.9	2,016.8	1,903.1	1,947.1
Total Hubbell Shareholders' Equity | Cumulative effect from adoption of CECL accounting standard (Note1)
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	13.6	19.1	13.4	18.3	13.4	18.3	18.3
Net income	1.5	1.9	1.6	3.4
Dividends to noncontrolling interest	(0.9)	(8.5)	(1.4)	(2.6)
Ending equity	$ 14.2	$ 12.5	$ 13.6	$ 19.1	$ 14.2	$ 12.5	$ 13.4