Consolidated Statements of Income (Unaudited) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Net sales	$ 883.1		$ 703.8
Cost of products sold	618.2		521.6
Gross Profit	264.9		182.2
Selling, general and administrative expenses	148.6		117.6
Impairment and restructuring charges	0.2	$ 0.2	1.7	$ 1.7	$ 0.0	$ 1.7
Operating Income (Loss)	116.1		62.9
Interest expense	(10.0)		(7.9)
Investment Income, Interest	0.4		0.6
Other (expense) income, net	2.3		(2.0)
Income (Loss) Before Income Taxes	108.8		53.6
Provision (benefit) for income taxes	28.3		15.5
Net Income	80.5		38.1
Net (loss) income attributable to noncontrolling interest	0.3		(0.1)
Net Income (loss) attributable to The Timken Company	$ 80.2		$ 38.2
Net Income per Common Share attributable to The Timken Company Common Shareholders
Basic earnings per share	$ 1.03		$ 0.49
Diluted earnings per share	1.02		0.48
Common Stock, Dividends, Per Share, Declared	$ 0.27		$ 0.26