Quarterly Results (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of Quarterly Results
Net sales	$ 239.2	$ 253.5	$ 257.5	$ 235.4	$ 234.1		$ 247.9		$ 243.2		$ 218.6		$ 985.6	$ 943.8	$ 826.3
Gross profit	61.9	69.8	74.7	64.7	62.2		70.4		61.8		57.9		271.1	252.3	214.2
Operating profit	17.5	28.1	31.1	21.4	20.4		25.8		20.9		19.0		98.1	86.1	69.0
Income (loss) from continuing operations	11.0	19.0	21.4	13.5	12.8		20.8		12.9		13.2		64.9	59.7	29.4
Income (loss) on discontinued operations	0	0	0	0	0		(1.3)		0.2		(0.1)		0	(1.2)	(0.9)
Net income (loss)	11.0	19.0	21.4	13.5	12.8		19.5		13.1		13.1		64.9	58.5	28.5
Net income (loss) attributable to noncontrolling interests	0	0	(0.3)	0.1	0		0		0		0		(0.2)	0	(0.7)
Net income (loss) attributable to AMCOL shareholders	11.0	19.0	21.7	13.4	12.8		19.5		13.1		13.1		65.1	58.5	29.2
Basic earnings per share attributable to AMCOL shareholders (in dollars per share)	$ 0.34	$ 0.59	$ 0.68	$ 0.42	$ 0.40	[1]	$ 0.61	[1]	$ 0.41	[1]	$ 0.42	[1]	$ 2.03	$ 1.85	$ 0.94
Diluted earnings per share attributable to AMCOL shareholders (in dollars per share)	$ 0.34	$ 0.59	$ 0.67	$ 0.41	$ 0.40	[1]	$ 0.61	[1]	$ 0.41	[1]	$ 0.41	[1]	$ 2.01	$ 1.82	$ 0.93
Performance Materials [Member]
Summary of Quarterly Results
Net sales	114.6	121.0	131.1	125.2	120.4		122.2		118.3		115.8		491.9	476.7	416.5
Gross profit	26.7	31.2	35.6	33.4	30.7		31.5		26.2		28.1
Operating profit	14.3	18.0	22.5	21.5	18.1		19.5		13.4		16.1		76.3	67.1	53.5
Construction Technologies [Member]
Summary of Quarterly Results
Net sales	50.2	60.6	61.4	50.9	54.4		71.0		74.8		51.7		223.1	251.9	225.5
Gross profit	15.1	20.1	18.7	14.6	14.6		21.8		22.2		15.3
Operating profit	1.4	7.0	6.3	0.9	0.5		7.0		8.0		1.8		15.6	17.3	20.4
Energy services [Member]
Summary of Quarterly Results
Net sales	71.8	69.1	61.1	55.3	53.9		50.1		45.1		45.6		257.3	194.7	153.6
Gross profit	18.8	17.7	19.2	15.4	15.4		15.4		11.7		13.5
Operating profit	8.3	7.9	7.7	4.8	6.1		5.8		3.7		5.7		28.7	21.3	13.7
Transportation [Member]
Summary of Quarterly Results
Net sales	10.5	10.7	11.7	11.1	11.7		14.9		14.8		12.7
Gross profit	1.1	1.1	1.2	1.2	1.3		1.8		1.6		1.4
Operating profit	0.1	0.2	0.3	0.2	0.3		0.7		0.7		0.5
Intersegment Sales/gross profit [Member]
Summary of Quarterly Results
Net sales	(7.9)	(7.9)	(7.8)	(7.1)	(6.3)		(10.3)		(9.8)		(7.2)		(30.7)	(33.6)	(21.5)
Gross profit	0.2	(0.3)	0	0.1	0.2		(0.1)		0.1		(0.4)
Corporate [Member]
Summary of Quarterly Results
Operating profit	$ (6.6)	$ (5.0)	$ (5.7)	$ (6.0)	$ (4.6)		$ (7.2)		$ (4.9)		$ (5.1)		$ (23.3)	$ (21.8)	$ (21.0)

[1] Earnings per share (EPS) for each quarter is computed using the weighted-average number of shares outstanding during the quarter, while EPS for the year is computed using the weighted-average number of shares outstanding during the year. Thus, the sum of the EPS for each of the four quarters may not equal the EPS for the year.