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Consolidated Condensed Statements of Comprehensive Income (Unaudited) (Parenthetical) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Consolidated Condensed Statements of Comprehensive Income [Abstract]    
Tax benefit of change in postretirement benefit plans $ 0 $ 11
Tax expense of net change in unrealized gains on investment securities   3
Tax benefit of amortization of prior service costs   0
Tax benefit of amortization of net actuarial loss 0 11
Tax (expense) benefit of amortization of net actuarial loss 0  
Tax benefit of unrealized losses arising during period   0
Tax expense of gains realized during the period   $ 3