v3.8.0.1

COMMITMENTS AND CONTINGENCIES (Tables) | 12 Months Ended
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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 |

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- Definition Tabular disclosure of the aggregate amount of payments due on known contractual obligations for the five years following the date of the latest balance sheet and the combined aggregate amount of maturities of known contractual obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K (SK) -Number 229 -Section 303 -Paragraph a -Subparagraph 5 + Details
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