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Fair Value Measurements Narrative (Details) (USD $)
In Millions, unless otherwise specified
 6 Months Ended 12 Months Ended
Jun. 30, 2012
Dec. 31, 2011
Dec. 31, 2010
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Risk premium adjustment assumption to project change in fair value of loan 1.00%    
Carrying value of property, plant and equipment impaired during the period $ 48 $ 124 $ 16
Impairment of property, plant, and equipment 19 32 7
Carrying value of intangibles impaired during the period 77 319 33
Impairment of intangible assets (Excluding goodwill) 15 39 4
Carrying Value of Asset Retirement Obligations Written Dow During the Period   4 1
Increase (Decrease) in Asset Retirement Obligations   0 1
Investment Segment [Member]
      
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Change in fair value of loan from 1 percent change in risk premium 3.00%    
Investment Segment [Member] | Fair Value, Inputs, Level 3 [Member]
      
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Unrealized losses included in earnings related to Level 3 investments 2    
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
      
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Fair value of property, plant, and equipment impaired during the period 29 92 9
Fair value of intangibles impaired during the period 62 280 29
Fair Value of Asset Retirement Obligations Written Down During the Period   (4) 0
ARO Fair Value after Impairment [Member]
      
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Increase (Decrease) in Asset Retirement Obligations   2  
ARO Fair Value after Impairment [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
      
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Fair Value of Asset Retirement Obligations Written Down During the Period   2  
ARO fair value incurred [Member]
      
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Increase (Decrease) in Asset Retirement Obligations   (2)  
ARO fair value incurred [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
      
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Fair Value of Asset Retirement Obligations Written Down During the Period   $ 2