Noncontrolling Interest (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Equity attributable to AMCOL's shareholders
Net income attributable to AMCOL shareholders	$ 58,521	[1]	$ 29,235	[1]	$ 32,042	[1]
Change from net income and transfers from noncontrolling interest
Decrease in additional paid-in capital for purchase of the remaining noncontrolling interest in Volclay South Africa (Proprietary) Limited	(5,702)	[1]	2,701	[1]	(5,528)	[1]
Decrease in additional paid-in capital for transfer of 26% interest in Batlhako	0	[1]
AMCOL Shareholders [Member]
Equity attributable to AMCOL's shareholders
Net income attributable to AMCOL shareholders	58,521	[1]
Change from net income and transfers from noncontrolling interest
Decrease in additional paid-in capital for purchase of the remaining noncontrolling interest in Volclay South Africa (Proprietary) Limited	(5,402)	[1]
Decrease in additional paid-in capital for transfer of 26% interest in Batlhako	(3,403)	[1]
Change from net income attributable to AMCOL shareholders and transfers from noncontrolling interest	$ 49,716	[1]

[1] Restated