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Asset Retirement Obligations Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2011
Asset Retirement Obligations [Abstract]  
Schedule of Change in Asset Retirement Obligation [Table Text Block]
Changes in AROs for the years ended December 31, 2011 and 2010, were as follows (in millions):
 
 
2011
 
2010
Balance at beginning of year (current and noncurrent)
 
$
30

 
$
34

Additions to accrual
 
3

 
2

Accretion expense
 
2

 
2

Settlements
 
(8
)
 
(7
)
Changes in timing and amount of estimated cash flows
 
(1
)
 
(1
)
Balance at end of year
 
$
26

 
$
30