v3.8.0.1
COMMITMENTS AND CONTINGENCIES (Tables)
12 Months Ended
Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]  
Schedule of Future Minimum Payments for Operating Leases and Purchase Obligations [Table Text Block]
Lessee Commitments. Future minimum rental payments applicable to all noncancellable operating leases and purchase obligations as of December 31, 2017 are as follows:
 
Payments Due by Period
 
2018
 
2019
 
2020
 
2021
 
2022
 
There-
after
 
Total
 
(Thousands of Dollars)
Operating leases
$
39,236

 
$
34,203

 
$
19,541

 
$
13,324

 
$
7,295

 
$
68,386

 
$
181,985

Purchase obligations
$
6,963

 
$
6,133

 
$
4,686

 
$
4,690

 
$
4,480

 
$
300

 
$
27,252