Summary of Significant Accounting Policies Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]  
Schedule of Asset Retirement Obligations [Table Text Block]
As of December 31, 2014 and 2013, our asset retirement obligations were as follows (in thousands):
 
2014
 
2013
Balance, January 1
$
49,879

 
$
102,465

New asset retirement obligations
8,718

 
18,292

Change in assumptions
(2,096
)
 
(75,900
)
Accretion
6,531

 
17,171

Settlement of asset retirement obligations
(9,844
)
 
323

Foreign currency translation and other
(9,650
)
 
(12,472
)
Balance, December 31
$
43,538

 
$
49,879