CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) [Abstract]
Net income (loss)	$ (26.6)	$ 19.0	$ 0.5	$ 53.9
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	1.3	7.8	(19.4)	4.3
Unrealized gain (loss) on available-for-sale securities	(1.6)	4.9	(4.3)	4.1
Unrealized gain (loss) on interest rate swap agreements	0.2	0	1.4	0
Pension adjustment	0.2	0.2	0.6	0.6
Total other comprehensive income (loss), net of tax	0.1	12.9	(21.7)	9.0
Total comprehensive income (loss) including noncontrolling interests	(26.5)	31.9	(21.2)	62.9
Less: Net income (loss) attributable to noncontrolling interests	(6.8)	0	(6.8)	(0.2)
Less: Foreign currency translation adjustments attributable to noncontrolling interests	(0.2)	0	(0.7)	(0.1)
Total comprehensive income (loss) attributable to noncontrolling interests	(7.0)	0	(7.5)	(0.3)
Total comprehensive income (loss) attributable to AMCOL shareholders	$ (19.5)	$ 31.9	$ (13.7)	$ 63.2