CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income (loss)	$ 18.8	$ 20.0	$ 53.4	$ 46.5
Other comprehensive income (loss):
Foreign currency translation adjustment	8.0	(22.4)	4.5	(20.2)
Unrealized gain (loss) on available-for-sale securities, net of tax	4.9	(1.6)	4.1	(8.2)
Unrealized gain (loss) on interest rate swap agreements, net of tax	0	(1.3)	0	(1.6)
Pension adjustment, net of tax	0.2	0.1	0.6	0.1
Comprehensive income (loss)	31.9	(5.2)	62.6	16.6
AMCOL Shareholders
Net income (loss)	18.8	20.1	53.6	46.6
Other comprehensive income (loss):
Foreign currency translation adjustment	8.0	(21.8)	4.6	(19.6)
Unrealized gain (loss) on available-for-sale securities, net of tax	4.9	(1.6)	4.1	(8.2)
Unrealized gain (loss) on interest rate swap agreements, net of tax	0	(1.3)	0	(1.6)
Pension adjustment, net of tax	0.2	0.1	0.6	0.1
Comprehensive income (loss)	31.9	(4.5)	62.9	17.3
Noncontrolling Interest
Net income (loss)	0	(0.1)	(0.2)	(0.1)
Other comprehensive income (loss):
Foreign currency translation adjustment	0	(0.6)	(0.1)	(0.6)
Unrealized gain (loss) on available-for-sale securities, net of tax	0	0	0	0
Unrealized gain (loss) on interest rate swap agreements, net of tax	0	0	0	0
Pension adjustment, net of tax	0	0	0	0
Comprehensive income (loss)	$ 0	$ (0.7)	$ (0.3)	$ (0.7)