Earnings Per Share (Computation Of Basic And Diluted Income Per Common Share From Continuing Operations) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Income (loss) from continuing operations attributable to OM Group, Inc. common stockholders	$ 8,068	$ (22,753)	$ (101,170)	$ (10,685)
Earnings per common share:
Income (loss) from continuing operations attributable to OM Group, Inc. common stockholders - basic (in dollars per share)	$ 0.26	$ (0.71)	$ (3.19)	$ (0.34)
Income (loss) from continuing operations attributable to OM Group, Inc. common stockholders - assuming dilution (in dollars per share)	$ 0.26	$ (0.71)	$ (3.19)	$ (0.34)
Weighted average shares outstanding - basic (in shares)	31,452	31,882	31,673	31,878
Dilutive effect of stock options and restricted stock	169	0	0	0
Weighted average shares outstanding - assuming dilution (in shares)	31,621	31,882	31,673	31,878