Industry Segments Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Sales:
Net sales	$ 829.7	$ 877.0	$ 874.0	$ 809.7	$ 848.8	$ 895.3	$ 855.8	$ 759.5	$ 3,390.4	$ 3,359.4	$ 3,183.9
Operating Income:
Operating Income									474.6	517.4	507.6
Interest expense									(31.0)	(31.2)	(30.8)
Income before income taxes									418.6	485.5	473.8
Assets:
Assets	3,208.7				3,320.1				3,208.7	3,320.1	3,184.0
Capital Expenditures:
Capital expenditures									77.1	60.3	58.8
Depreciation and Amortization:
Depreciation and amortization									85.2	79.2	70.6
Operating Segments | Electrical
Net Sales:
Net sales									2,388.3	2,398.2	2,262.6
Operating Income:
Operating Income									279.0	337.9	341.1
Assets:
Assets	2,120.9				1,963.0				2,120.9	1,963.0	1,813.8
Capital Expenditures:
Capital expenditures									47.9	35.1	32.4
Depreciation and Amortization:
Depreciation and amortization									56.2	53.4	48.0
Operating Segments | Power
Net Sales:
Net sales									1,002.1	961.2	921.3
Operating Income:
Operating Income									195.6	179.5	166.5
Assets:
Assets	839.7				832.0				839.7	832.0	707.0
Capital Expenditures:
Capital expenditures									28.4	21.8	25.0
Depreciation and Amortization:
Depreciation and amortization									29.0	25.8	22.6
Segment Reconciling Items
Operating Income:
Interest expense									(31.0)	(31.2)	(30.8)
Investment income and other expense, net									(25.0)	(0.7)	(3.0)
Corporate, Non-Segment | General Corporate
Assets:
Assets	$ 248.1				$ 525.1				248.1	525.1	663.2
Capital Expenditures:
Capital expenditures									$ 0.8	$ 3.4	$ 1.4