v2.4.0.8
Clearing Operations (Schedule of Derivative Contracts Outstanding) (Details) (USD $)
In Millions, unless otherwise specified
Sep. 30, 2013
contract
Sep. 30, 2012
contract
Clearing Operations [Line Items]    
Market value of derivative contracts $ 1,359  
Total Number of Cleared Contracts 74,849,697 81,799,340
Commodity forwards and options [Member]
    
Clearing Operations [Line Items]    
Market value of derivative contracts 769 [1],[2]  
Total Number of Cleared Contracts 624,714 [3] 644,589 [3]
Fixed-income options and futures [Member]
    
Clearing Operations [Line Items]    
Market value of derivative contracts 297 [2],[4]  
Total Number of Cleared Contracts 21,131,906 26,586,488
Stock options and futures [Member]
    
Clearing Operations [Line Items]    
Market value of derivative contracts 125 [2],[4]  
Total Number of Cleared Contracts 23,200,139 21,735,025
Index options and futures [Member]
    
Clearing Operations [Line Items]    
Market value of derivative contracts $ 168 [2],[4]  
Total Number of Cleared Contracts 29,892,938 32,833,238
[1] We determined the fair value of our forward contracts using standard valuation models that were based on market-based observable inputs including LIBOR rates and the spot price of the underlying instrument.
[2] We determined the fair value of our option contracts using standard valuation models that were based on market-based observable inputs including implied volatility, interest rates and the spot price of the underlying instrument.
[3] The total volume in cleared power related to commodity contracts was 1,247 Terawatt hours (TWh) for the nine months ended September 30, 2013 and 1,250 TWh for the nine months ended September 30, 2012.
[4] We determined the fair value of our futures contracts based upon quoted market prices and average quoted market yields.