EARNINGS PER COMMON SHARE: (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
EPS Numerator:
Net income attributable to Rockwood Holdings, Inc. shareholders	$ 18.9	$ 75.8
EPS Denominator:
Basic weighted average number of common shares outstanding	78,530	77,384
Effect of dilutive stock options and other incentives (in shares)	1,558	2,931
Diluted weighted average number of common shares outstanding and common stock equivalents	80,088	80,315
Basic earnings per common share attributable to Rockwood Holdings, Inc. shareholders: (in dollars per share)	$ 0.24	$ 0.98
Diluted earnings per common share attributable to Rockwood Holdings, Inc. shareholders: (in dollars per share)	$ 0.24	$ 0.94
Number of outstanding shares that have an anti-dilutive effect	0	0