Consolidated Statements of Income (Unaudited) - USD ($) $ in Millions	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net sales	$ 906.3		$ 750.6		$ 1,789.4	$ 1,454.4
Cost of products sold	638.9		549.5		1,257.1	1,071.1	$ 2,191.7	$ 1,963.5	$ 2,068.5
Gross Profit	267.4		201.1		532.3	383.3
Selling, general and administrative expenses	141.8		123.9		290.4	241.5	508.3	440.2	484.6
Impairment and restructuring charges	0.3	$ 0.3	0.8	$ 0.8	0.5	2.5		2.5
Operating Income (Loss)	125.3		76.4		241.4	139.3	299.5	244.4	333.2
Interest expense	(10.7)		(8.5)		(20.7)	(16.4)
Investment Income, Interest	0.5		0.7		0.9	1.3
Other (expense) income, net	7.0		5.3		9.3	3.3	$ (5.4)	$ (70.8)	$ (84.8)
Income (Loss) Before Income Taxes	122.1		73.9		230.9	127.5
Provision (benefit) for income taxes	30.2		(8.1)		58.5	7.4
Net Income	91.9		82.0		172.4	120.1
Net (loss) income attributable to noncontrolling interest	0.9		(0.5)		1.2	(0.6)
Net Income (loss) attributable to The Timken Company	$ 91.0		$ 82.5		$ 171.2	$ 120.7
Net Income per Common Share attributable to The Timken Company Common Shareholders
Basic earnings per share	$ 1.18		$ 1.06		$ 2.21	$ 1.55
Diluted earnings per share	1.16		1.04		2.17	1.53
Common Stock, Dividends, Per Share, Declared	$ 0.28		$ 0.27		$ 0.55	$ 0.53