v2.4.0.6
Clearing Operations (Schedule of Derivative Contracts Outstanding) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2013
contract
Mar. 31, 2012
contract
Clearing Operations [Line Items]    
Market value of derivative contracts $ 1,448  
Total Number of Cleared Contracts 27,882,196 30,687,619
Commodity forwards and options [Member]
    
Clearing Operations [Line Items]    
Market value of derivative contracts 784 [1],[2]  
Total Number of Cleared Contracts 236,276 [3] 294,614 [3]
Fixed-income options and futures [Member]
    
Clearing Operations [Line Items]    
Market value of derivative contracts 353 [2],[4]  
Total Number of Cleared Contracts 8,827,632 10,851,785
Stock options and futures [Member]
    
Clearing Operations [Line Items]    
Market value of derivative contracts 180 [2],[4]  
Total Number of Cleared Contracts 8,487,497 8,354,235
Index options and futures [Member]
    
Clearing Operations [Line Items]    
Market value of derivative contracts $ 131 [2],[4]  
Total Number of Cleared Contracts 10,330,791 11,186,985
[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 460 Terawatt hours (TWh) for the three months ended March 31, 2013 and 521 TWh for the three months ended March 31, 2012.
[4] We determined the fair value of our futures contracts based upon quoted market prices and average quoted market yields.