XML 89 R72.htm IDEA: XBRL DOCUMENT v2.4.0.6
Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Details)
Dec. 31, 2012
T
Dec. 31, 2011
T
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Coal [Member]
    
Derivative [Line Items]    
Quantity 135,000,000 [1] 147,000,000 [1]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Natural Gas [Member]
    
Derivative [Line Items]    
Quantity 20,000,000 [1] 50,000,000 [1]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 90,000,000 [1] 73,000,000 [1]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Renewable energy credits [Member]
    
Derivative [Line Items]    
Quantity 16,000,000 [1],[2] 17,000,000 [1],[2]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Uranium [Member]
    
Derivative [Line Items]    
Quantity 5,142,000 [1] 5,553,000 [1]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Ameren Missouri [Member] | Coal [Member]
    
Derivative [Line Items]    
Quantity 96,000,000 [1] 116,000,000 [1]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Ameren Missouri [Member] | Natural Gas [Member]
    
Derivative [Line Items]    
Quantity 4,000,000 [1] 8,000,000 [1]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Ameren Missouri [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 3,000,000 [1] 1,000,000 [1]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Ameren Missouri [Member] | Renewable energy credits [Member]
    
Derivative [Line Items]    
Quantity 3,000,000 [1],[2] 4,000,000 [1],[2]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Ameren Illinois [Member] | Natural Gas [Member]
    
Derivative [Line Items]    
Quantity 16,000,000 [1] 42,000,000 [1]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Ameren Illinois [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 21,000,000 [1] 11,000,000 [1]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Ameren Illinois [Member] | Renewable energy credits [Member]
    
Derivative [Line Items]    
Quantity 12,000,000 [1],[2] 12,000,000 [1],[2]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Other [Member] | Coal [Member]
    
Derivative [Line Items]    
Quantity 39,000,000 [1],[3] 31,000,000 [1],[3]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Other [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 66,000,000 [1],[3] 61,000,000 [1],[3]
Accrual and Normal Purchases and Normal Sales Contracts [Member] | Other [Member] | Renewable energy credits [Member]
    
Derivative [Line Items]    
Quantity 1,000,000 [1],[2],[3] 1,000,000 [1],[2],[3]
Cash Flow Hedges [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 9,000,000 [4] 17,000,000 [4]
Cash Flow Hedges [Member] | Other [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 9,000,000 [3],[4] 17,000,000 [3],[4]
Other Contract [Member] | Coal [Member]
    
Derivative [Line Items]    
Quantity 7,000,000 [5]  
Other Contract [Member] | Fuel Oils [Member]
    
Derivative [Line Items]    
Quantity 52,000,000 [5],[6] 36,000,000 [5],[6]
Other Contract [Member] | Natural Gas [Member]
    
Derivative [Line Items]    
Quantity 47,000,000 [5] 17,000,000 [5]
Other Contract [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 36,000,000 [5] 31,000,000 [5]
Other Contract [Member] | Ameren Missouri [Member] | Coal [Member]
    
Derivative [Line Items]    
Quantity    [5]  
Other Contract [Member] | Ameren Missouri [Member] | Natural Gas [Member]
    
Derivative [Line Items]    
Quantity    [5] 9,000,000 [5]
Other Contract [Member] | Ameren Missouri [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 2,000,000 [5] 1,000,000 [5]
Other Contract [Member] | Other [Member] | Coal [Member]
    
Derivative [Line Items]    
Quantity 7,000,000 [3],[5]  
Other Contract [Member] | Other [Member] | Fuel Oils [Member]
    
Derivative [Line Items]    
Quantity 52,000,000 [3],[5],[6] 36,000,000 [3],[5],[6]
Other Contract [Member] | Other [Member] | Natural Gas [Member]
    
Derivative [Line Items]    
Quantity 47,000,000 [3],[5] 8,000,000 [3],[5]
Other Contract [Member] | Other [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 34,000,000 [3],[5] 30,000,000 [3],[5]
Derivatives That Qualify for Regulatory Deferral [Member] | Fuel Oils [Member]
    
Derivative [Line Items]    
Quantity 26,000,000 [6],[7] 53,000,000 [6],[7]
Derivatives That Qualify for Regulatory Deferral [Member] | Natural Gas [Member]
    
Derivative [Line Items]    
Quantity 147,000,000 [7] 193,000,000 [7]
Derivatives That Qualify for Regulatory Deferral [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 23,000,000 [7] 21,000,000 [7]
Derivatives That Qualify for Regulatory Deferral [Member] | Uranium [Member]
    
Derivative [Line Items]    
Quantity 446,000 [7] 148,000 [7]
Derivatives That Qualify for Regulatory Deferral [Member] | Ameren Missouri [Member] | Fuel Oils [Member]
    
Derivative [Line Items]    
Quantity 26,000,000 [6],[7] 53,000,000 [6],[7]
Derivatives That Qualify for Regulatory Deferral [Member] | Ameren Missouri [Member] | Natural Gas [Member]
    
Derivative [Line Items]    
Quantity 19,000,000 [7] 19,000,000 [7]
Derivatives That Qualify for Regulatory Deferral [Member] | Ameren Missouri [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 9,000,000 [7] 6,000,000 [7]
Derivatives That Qualify for Regulatory Deferral [Member] | Ameren Illinois [Member] | Natural Gas [Member]
    
Derivative [Line Items]    
Quantity 128,000,000 [7] 174,000,000 [7]
Derivatives That Qualify for Regulatory Deferral [Member] | Ameren Illinois [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity 14,000,000 [7] 24,000,000 [7]
Derivatives That Qualify for Regulatory Deferral [Member] | Other [Member] | Power [Member]
    
Derivative [Line Items]    
Quantity    [3],[7] (9,000,000) [3],[7]
[1] Accrual contracts include commodity contracts that do not qualify as derivatives. As of December 31, 2012, these contracts ran through December 2017, March 2015, September 2035, May 2032, and October 2024 for coal, natural gas, power, renewable energy credits, and uranium, respectively.
[2] A renewable energy credit is created for every megawatthour of renewable energy generated. Ameren contracts include renewable energy credits from solar, wind, and landfill gas-generated power.
[3] Includes AERG and Genco contracts for coal and fuel oils, Marketing Company and Genco contracts for natural gas, Marketing Company contracts for power and renewable energy credits, and intercompany eliminations for power.
[4] As of December 31, 2012, these contracts ran through December 2016 for power.
[5] As of December 31, 2012, these contracts ran through December 2015, October 2016, April 2015, and December 2016 for coal, fuel oils, natural gas, and power, respectively.
[6] Fuel oils consist of heating and crude oil.
[7] As of December 31, 2012, these contracts ran through October 2015, March 2017, May 2032, and September 2014 for fuel oils, natural gas, power, and uranium, respectively.