GOODWILL: (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Goodwill
Balance at beginning of period	$ 864.8
Accumulated impairment	717.5	(717.5)
Foreign exchange	(23.6)
Balance at end of period	841.2
Gross amount of goodwill	1,558.7	1,582.3
Lithium
Goodwill
Balance at beginning of period	263.7
Foreign exchange	(7.5)
Balance at end of period	256.2
Gross amount of goodwill	256.2	263.7
Surface Treatment
Goodwill
Balance at beginning of period	342.1
Foreign exchange	(8.6)
Balance at end of period	333.5
Gross amount of goodwill	333.5	342.1
Performance Additives
Goodwill
Accumulated impairment	456.6	(456.6)
Gross amount of goodwill	456.6	456.6
Titanium Dioxide Pigments
Goodwill
Accumulated impairment	247.7	(247.7)
Gross amount of goodwill	247.7	247.7
Advanced Ceramics
Goodwill
Balance at beginning of period	254.3
Foreign exchange	(7.4)
Balance at end of period	246.9
Gross amount of goodwill	246.9	254.3
Corporate and other
Goodwill
Balance at beginning of period	4.7
Accumulated impairment	13.2	(13.2)
Foreign exchange	(0.1)
Balance at end of period	4.6
Gross amount of goodwill	$ 17.8	$ 17.9