v3.8.0.1
EMPLOYEE BENEFIT PLANS (Tables)
3 Months Ended
Mar. 31, 2018
Retirement Benefits [Abstract]  
Schedule of Net Benefit Costs [Table Text Block]
The components of net periodic benefit cost (income) related to our Pension Plans and other postretirement benefit plans were as follows:
 
Pension Plans
 
Other Postretirement Benefit Plans
 
2018
 
2017
 
2018
 
2017
 
(Thousands of Dollars)
For the three months ended March 31:
 
 
 
 
 
 
 
Service cost
$
2,406

 
$
2,239

 
$
126

 
$
113

Interest cost
1,206

 
1,127

 
108

 
108

Expected return on assets
(1,855
)
 
(1,603
)
 

 

Amortization of prior service credit
(514
)
 
(515
)
 
(287
)
 
(286
)
Amortization of net loss
544

 
371

 
54

 
48

Net periodic benefit cost (income)
$
1,787

 
$
1,619

 
$
1

 
$
(17
)