CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) [Abstract]
Net income (loss)	$ 10.4	$ 13.5
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	(9.9)	10.7
Unrealized gain (loss) on available-for-sale securities	(4.7)	(0.9)
Unrealized gain (loss) on interest rate swap agreements	0.4	0.2
Pension adjustment	0.4	0.2
Total other comprehensive income (loss), net of tax	(13.8)	10.2
Total comprehensive income (loss) including noncontrolling interests	(3.4)	23.7
Less: Net income (loss) attributable to noncontrolling interests	(0.1)	0.1
Less: Foreign currency translation adjustments attributable to noncontrolling interests	(0.2)	0.2
Total comprehensive income (loss) attributable to noncontrolling interests	(0.3)	0.3
Total comprehensive income (loss) attributable to AMCOL shareholders	$ (3.1)	$ 23.4