Industry Segments Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Sales:
Net sales	$ 854.2	$ 907.4	$ 908.8	$ 834.8	$ 829.7	$ 877.0	$ 874.0	$ 809.7	$ 3,505.2	$ 3,390.4	$ 3,359.4
Operating Income:
Operating Income									477.8	474.6	517.4
Interest expense									(43.4)	(31.0)	(31.2)
Income before income taxes									430.4	418.6	485.5
Assets:
Assets	3,525.0				3,208.7				3,525.0	3,208.7	3,320.1
Capital Expenditures:
Capital expenditures									67.2	77.1	60.3
Depreciation and Amortization:
Depreciation and amortization									92.3	85.2	79.2
Operating Segments | Electrical
Net Sales:
Net sales									2,460.2	2,388.3	2,398.2
Operating Income:
Operating Income									267.4	279.0	337.9
Assets:
Assets	2,246.0				2,120.9				2,246.0	2,120.9	1,963.0
Capital Expenditures:
Capital expenditures									43.4	47.9	35.1
Depreciation and Amortization:
Depreciation and amortization									61.2	56.2	53.4
Operating Segments | Power
Net Sales:
Net sales									1,045.0	1,002.1	961.2
Operating Income:
Operating Income									210.4	195.6	179.5
Assets:
Assets	911.5				839.7				911.5	839.7	832.0
Capital Expenditures:
Capital expenditures									22.7	28.4	21.8
Depreciation and Amortization:
Depreciation and amortization									31.1	29.0	25.8
Segment Reconciling Items
Operating Income:
Interest expense									(43.4)	(31.0)	(31.2)
Investment income and other expense, net									(4.0)	(25.0)	(0.7)
General Corporate, non-segment
Assets:
Assets	$ 367.5				$ 248.1				367.5	248.1	525.1
Capital Expenditures:
Capital expenditures									$ 1.1	$ 0.8	$ 3.4