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Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]  
Schedule of Asset Retirement Obligations [Table Text Block]
The following table provides asset retirement obligation activity for the years ended December 31, 2014 and 2013 (dollars in millions):
 
 
2014
 
2013
Asset retirement obligation at January 1
 
$
56

 
$
55

Accretion expense
 
8

 
7

Liabilities assumed in tw telecom acquisition
 
22

 
—

Liabilities settled
 
(7
)
 
(6
)
Revision in estimated cash flows
 
7

 
—

Effect of foreign currency rate change
 
(1
)
 
—

Asset retirement obligation at December 31
 
$
85

 
$
56