EMPLOYEE BENEFIT PLANS - Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 27	$ 67,542
Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		27
Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Pension Benefits | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		27
Pension Benefits | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		27
Pension Benefits | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,066	10,369	$ 10,693
Postretirement Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,066	5,835
Postretirement Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	4,534
Postretirement Benefits | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10
Postretirement Benefits | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10
Postretirement Benefits | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Postretirement Benefits | United States equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	180	4,185
Postretirement Benefits | United States equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	180	4,185
Postretirement Benefits | United States equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Postretirement Benefits | Global equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,158	1,650
Postretirement Benefits | Global equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,158	1,650
Postretirement Benefits | Global equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Postretirement Benefits | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,718	4,534
Postretirement Benefits | Fixed income | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,718	0
Postretirement Benefits | Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 4,534