Noncontrolling Interest (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			3 Months Ended							12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 AMCOL Shareholders [Member]	Sep. 30, 2011 AMCOL Shareholders [Member]	Jun. 30, 2011 AMCOL Shareholders [Member]	Mar. 31, 2011 AMCOL Shareholders [Member]	Dec. 31, 2010 AMCOL Shareholders [Member]	Sep. 30, 2010 AMCOL Shareholders [Member]	Mar. 31, 2010 AMCOL Shareholders [Member]	Dec. 31, 2011 AMCOL Shareholders [Member]
Equity attributable to AMCOL's shareholders
Net income attributable to AMCOL shareholders	$ 59,111	$ 30,347	$ 34,799	$ 13,696	$ 19,425	$ 13,755	$ 12,235	$ (9,347)	$ 17,417	$ 6,128	$ 59,111
Change from net income and transfers from noncontrolling interest
Purchase of noncontrolling interest shares	(5,735)	2,701	(5,528)								(5,189)
Decrease in additional paid-in capital for transfer of 26% interest in Batlhako	0										(3,403)
Change from net income attributable to AMCOL shareholders and transfers from noncontrolling interest											$ 50,519