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Gas Reserves (Tables)
 12 Months Ended
Dec. 31, 2016
Gas Reserves [Abstract]  
Gas Reserves Table [Text Block]
In thousands
 
2016
 
2015
Gas reserves, current
 
$
15,926

 
$
17,094

Gas reserves, non-current
 
171,610

 
170,453

Less: Accumulated amortization
 
71,426

 
55,901

Total gas reserves(1)
 
116,110

 
131,646

Less: Deferred taxes on gas reserves
 
28,119

 
27,203

Net investment in gas reserves
 
$
87,991

 
$
104,443