Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated other comprehensive income loss [Abstract]
Cumulative foreign currency translation	$ (19.1)				$ 6.0				$ (19.1)	$ 6.0
Prior service cost on pension plans (net of tax benefit of $0.1 in 2013 and $0.1 in 2012)	(0.1)				(0.2)				(0.1)	(0.2)
Net actuarial loss on pension plans (net of tax benefit of $2.7 in 2013 and $7.8 in 2012)	(4.2)				(12.0)				(4.2)	(12.0)
Unrealized loss on interest rate swap agreement (net of tax benefit of $2.1 in 2013 and $3.3 in 2012)	(3.3)				(5.1)				(3.3)	(5.1)
Unrealized gain on available-for-sale securities (net of tax expense of $1.2 in 2012)	0				12.1				0	12.1
Accumulated other comprehensive income (loss)	(26.7)				0.8				(26.7)	0.8
Cumulative foreign currency translation, tax benefit	1.3								1.3
Prior service cost on pension plans, tax benefit	0.1				0.1				0.1	0.1
Net actuarial loss on pension plans, tax benefit	2.7				7.8				2.7	7.8
Unrealized loss on interest rate swap agreement, tax benefit	2.1				3.3				2.1	3.3
Unrealized gain on available-for-sale securities, tax benefit					1.2					1.2
Pre-Tax Amount [Abstract]
Foreign currency translation adjustment									(26.9)	5.2	(24.8)
Available-for-sale securities, Unrealized gain (loss) on available-for-sale securities									(0.7)	10.8	(10.3)
Available for sale of securities, Reclassification of net (gains) losses to net income									(12.6)	0	0
Interest rate swap agreements, Unrealized gain (loss) arising during period									0.3	(1.7)	(5.0)
Reclassification of net (gain) loss to on interest rate swaps, pre-tax amount									2.6	2.3	2.6
Net actuarial gains (losses) and prior service costs arising during the period									11.8	(2.1)	(13.6)
Amortization of net actuarial (gains) losses and prior service costs									1.2	1.2	0.2
Total other comprehensive income (loss), Pre-Tax Amount									(24.3)	15.7	(50.9)
Tax (Expense) Benefit [Abstract]
Foreign currency translation adjustment									1.3	0	0
Unrealized gain (loss) on available-for-sale securities									0.2	(1.2)	1.0
Unrealized gain on available for sale securities, during period, tax									1.0	0	0
Interest rate swap agreements, Unrealized gain (loss) arising during period									(0.1)	0.1	1.9
Interest rate swap agreements, Reclassification of net (gain) loss to net income									(1.0)	(0.1)	(1.0)
Net actuarial gains (losses) and prior service costs arising during the period									(4.6)	1.9	5.0
Amortization of net actuarial (gains) losses and prior service costs									(0.5)	(1.1)	(0.1)
Total other comprehensive income (loss), Tax (Expense) Benefit									(3.7)	(0.4)	6.8
Net-Of-Tax Amount [Abstract]
Foreign currency translation adjustment									(25.6)	5.2	(24.8)
Unrealized gain (loss) on available-for-sale securities									(0.5)	9.6	(9.3)
Unrealized gain(loss) on available sale of securities net of Tax									(11.6)	0	0
Interest rate swap agreements, Unrealized gain (loss) arising during period									0.2	(1.6)	(3.1)
Interest rate swap agreements, Reclassification of net (gain) loss to net income									1.6	2.2	1.6
Net actuarial gains (losses) and prior service costs arising during the period									7.2	(0.2)	(8.6)
Amortization of net actuarial (gains) losses and prior service costs									0.7	0.1	0.1
Total other comprehensive income (loss), net of tax									(28.0)	15.3	(44.1)
Schedule Of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of available-for-sale securities									12.6	0	0
Interest expense, net									(10.3)	(10.4)	(11.0)
Income tax expense									(11.0)	(23.3)	(20.8)
Net income (loss) attributable to AMCOL shareholders	22.9	(19.8)	16.6	10.5	11.0	19.0	21.7	13.4	30.2	65.1	58.5
Reclassification out of Accumulated Other Comprehensive Income [Member]
Schedule Of Accumulated Other Comprehensive Income [Line Items]
Net income (loss) attributable to AMCOL shareholders									(9.3)	2.3	1.7
Reclassification out of Accumulated Other Comprehensive Income [Member] | Available-for-sale Securities [Member]
Schedule Of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of available-for-sale securities									(12.6)	0	0
Income tax expense									1.0	0	0
Net income (loss) attributable to AMCOL shareholders									(11.6)	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Swaps [Member]
Schedule Of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net									2.6	2.3	2.6
Income tax expense									(1.0)	(0.1)	(1.0)
Net income (loss) attributable to AMCOL shareholders									1.6	2.2	1.6
Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of Pension Items [Member]
Schedule Of Accumulated Other Comprehensive Income [Line Items]
Components of net periodic benefit cost									1.2	1.2	0.2
Income tax expense									(0.5)	(1.1)	(0.1)
Net income (loss) attributable to AMCOL shareholders									$ 0.7	$ 0.1	$ 0.1