Earnings Per Share (Computation Of Basic And Diluted Net Income Per Common Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share [Abstract]
Net income (loss) attributable to OM Group, Inc. common stockholders	$ (22,339)	$ 24,620	$ (10,390)	$ 55,272
Weighted average shares outstanding - basic (in shares)	31,882	30,535	31,878	30,531
Dilutive effect of stock options and restricted stock (in shares)	0	186	0	177
Weighted average shares outstanding - assuming dilution (in shares)	31,882	30,721	31,878	30,708
Earnings per common share:
Net income (loss) attributable to OM Group, Inc. common stockholders - basic (in dollars per share)	$ (0.70)	$ 0.81	$ (0.33)	$ 1.81
Net income (loss) attributable to OM Group, Inc. common stockholders - assuming dilution (in dollars per share)	$ (0.70)	$ 0.80	$ (0.33)	$ 1.80