Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary Of Significant Accounting Policies [Abstract]
Minimum percentage at which subsidiaries consolidated	50.00%
Percentage of revenue elimination	77.00%	100.00%	100.00%

Minimum percentage at which subsidiaries consolidated.

No definition available.

Name:	aco_MinimumPercentageAtWhichSubsidiariesConsolidated
Namespace Prefix:	aco_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration