Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2011

Summary of Significant Accounting Policies [Abstract]

Revenue by segment

The composition of consolidated revenues by segment is as follows:

	Percentage of Net Sales
	2011 Restated			2010 Restated			2009 Restated
Minerals and materials		51	%		50	%		49	%
Environmental		27	%		27	%		29	%
Oilfield services		21	%		19	%		17	%
Transportation		6	%		6	%		7	%
Intersegment sales		-5	%		-2	%		-2	%
		100	%		100	%		100	%

Reconciliation between basic and diluted earnings per share

   Basic earnings per share is computed by dividing net income attributable to AMCOL shareholders by the weighted average number of common shares outstanding. Diluted earnings per share is similarly computed, except the denominator is increased to include the dilutive effects of stock compensation awards and other share equivalents. Stock compensation awards are antidilutive and therefore excluded from our diluted earnings per share calculation when their exercise would result in a net decrease in the weighted average number of common shares outstanding. A reconciliation between the shares used to compute basic and diluted earnings per share follows:

	2011		2010		2009
Weighted average common shares outstanding for the year		31,708,949		31,178,813		30,764,282
Dilutive impact of stock equivalents		436,824		368,778		269,432
Weighted average common and common equivalent shares for the year		32,145,773		31,547,591		31,033,714
Common shares outstanding at December 31		31,728,969		31,032,791		30,773,908
Weighted average anti-dilutive shares excluded from the computation of diluted earnings per share		189,768		470,097		938,546