EMPLOYEE BENEFIT PLANS - Allocation of Plan Assets of the Defined Benefit Pension Plan By Category (Details) - Qualified Plan - Qualified Pension Plan - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Target Allocation for 2018
Target allocation (as a percent)	100.00%
Allocation of plan assets of defined benefit pension plan by category
Total (as a percent)	100.00%	100.00%
Employer contributions	$ 43,500	$ 20,889
Cash and cash equivalents
Target Allocation for 2018
Target allocation (as a percent)	2.00%
Allocation of plan assets of defined benefit pension plan by category
Total (as a percent)	15.00%	2.00%
Equity securities
Target Allocation for 2018
Target allocation (as a percent)	60.00%
Allocation of plan assets of defined benefit pension plan by category
Total (as a percent)	55.00%	61.00%
Fixed income
Target Allocation for 2018
Target allocation (as a percent)	38.00%
Allocation of plan assets of defined benefit pension plan by category
Total (as a percent)	30.00%	37.00%

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(ii)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- References

No definition available.

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

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- Definition

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2446-114920

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-Publisher FASB
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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