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Employee Benefits (Tables)
3 Months Ended
Mar. 31, 2017
Employee Benefits [Abstract]  
Components of Net Periodic Benefit Cost for Postretirement Benefit Plans
The components of net periodic benefit cost for our postretirement benefit plans for the three months ended March 31, 2017 and 2016 were as follows (in thousands):

  
Three Months Ended
March 31,
 
Postretirement benefits
 
2017
  
2016
 
Service cost
 
$
  
$
 
Interest cost
  
2
   
3
 
Amortization of prior service cost
  
   
(13
)
Actuarial net (gain) loss
  
(59
)
  
275
 
Net periodic benefit cost (credit)
 
$
(57
)
 
$
265