Earnings Per Share (Computation Of Basic And Diluted Net Income Per Common Share) (Details) (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Earnings Per Share [Abstract]
Net income (loss) attributable to OM Group, Inc. common stockholders	$ (68,254)	$ 24,201	$ (12,982)	$ 59,590
Weighted average shares outstanding - basic	31,382	30,474	30,817	30,417
Dilutive effect of stock options and restricted stock		86		118
Weighted average shares outstanding - assuming dilution	31,382	30,560	30,817	30,535
Net income (loss) attributable to OM Group, Inc. common stockholders - basic	$ (2.17)	$ 0.79	$ (0.42)	$ 1.96
Net income (loss) attributable to OM Group, Inc. common stockholders - assuming dilution	$ (2.17)	$ 0.79	$ (0.42)	$ 1.95