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Employee Postretirement Benefits Employee Postretirement Benefits (Tables)
 9 Months Ended
Oct. 31, 2018
Retirement Benefits [Abstract]  
Components of net periodic benefit cost for postretirement plan The components of the net periodic benefit cost for postretirement benefits are as follows:
 
Three Months Ended
 
Nine Months Ended
 
October 31,
2018
 
October 31,
2017
 
October 31,
2018
 
October 31,
2017
Service cost
$
7

 
$
21

 
$
21

 
$
64

Interest cost
79

 
83

 
237

 
247

Amortization of actuarial losses
32

 
30

 
96

 
90

Amortization of unrecognized gains in prior service cost
(40
)
 
(40
)
 
(120
)
 
(120
)
Net periodic benefit cost
$
78

 
$
94

 
$
234

 
$
281