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'Monetary' elements on report '040502 - Disclosure - Acquisitions and Other Transactions (Schedule of Aggregate Purchase Consideration Paid and the Amount of Assets Acquired) (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '040601 - Disclosure - Long-Term Obligations (Narrative) (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '040602 - Disclosure - Long-Term Obligations (Long-Term Financing Arrangements) (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '040901 - Disclosure - Derivative Financial Instruments (Narrative) (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '041001 - Disclosure - Fair Value Measurements (Narrative) (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '041101 - Disclosure - Income Taxes (Narrative) (Details)' had a mix of different decimal attribute values. 'Shares' elements on report '041201 - Disclosure - Stock-Based Compensation (Narrative) (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '041201 - Disclosure - Stock-Based Compensation (Narrative) (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '041301 - Disclosure - Stockholders' Equity (Narrative) (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '041601 - Disclosure - Commitments And Contingencies (Narrative) (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '042101 - Disclosure - Subsequent Events (Details)' had a mix of different decimal attribute values. Process Flow-Through: 000100 - Statement - CONSOLIDATED BALANCE SHEETS Process Flow-Through: Removing column 'Dec. 31, 2010' Process Flow-Through: Removing column 'Dec. 31, 2009' Process Flow-Through: 000105 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical) Process Flow-Through: 000200 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2012' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2012' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2012' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2012' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2011' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2011' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2011' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2011' Process Flow-Through: 000205 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) Process Flow-Through: 000250 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2012' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2012' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2012' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2012' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2011' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2011' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2011' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2011' Process Flow-Through: 000251 - Statement - CONSOLIDATED STATMENT OF COMPREHENSIVE INCOME (Parenthetical) Process Flow-Through: 000400 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS amt-20121231.xml amt-20121231.xsd amt-20121231_cal.xml amt-20121231_def.xml amt-20121231_lab.xml amt-20121231_pre.xml true true