Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2012

Summary of Significant Accounting Policies [Abstract]

Revenue by segment

The composition of consolidated revenues by segment is as follows:

	Percentage of Net Sales
	2012			2011			2010
Performance materials		50	%		51	%		50	%
Construction technologies		23	%		27	%		27	%
Energy services		26	%		21	%		19	%
Transportation		4	%		6	%		6	%
Intersegment sales		-3	%		-5	%		-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:

	2012		2011		2010
Weighted average common shares outstanding for the year		32,050,538		31,708,949		31,178,813
Dilutive impact of stock equivalents		347,827		436,824		368,778
Weighted average common and common equivalent shares for the year		32,398,365		32,145,773		31,547,591
Common shares outstanding at December 31		32,184,110		31,728,969		31,032,791
Weighted average anti-dilutive shares excluded from the computation of diluted earnings per share		402,485		189,768		470,097