PENSION AND OTHER POST-RETIREMENT BENEFIT PLANS - SCHEDULE OF PENSION PLAN ASSETS WITHIN THE FAIR VALUE HIERARCHY (Details) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 1,053,438	$ 963,861	$ 1,086,226
Fair Value, Measurements, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,053,438	963,861
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	1,039,879	944,964
Fair Value, Measurements, Recurring | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	365	1,040
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	13,194	17,857
Fair Value, Measurements, Recurring | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	14,188	19,561
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	629	664
Fair Value, Measurements, Recurring | Cash and cash equivalents | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	365	1,040
Fair Value, Measurements, Recurring | Cash and cash equivalents | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	13,194	17,857
Fair Value, Measurements, Recurring | Cash and cash equivalents | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global all-cap
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	248,222	210,850
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	248,222	210,850
Fair Value, Measurements, Recurring | Global all-cap | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global all-cap | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global all-cap | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | U.S. government/agency
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	264,066	242,618
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	264,066	242,618
Fair Value, Measurements, Recurring | U.S. government/agency | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | U.S. government/agency | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | U.S. government/agency | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	136,896	117,656
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	136,896	117,656
Fair Value, Measurements, Recurring | Corporate bonds | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Corporate bonds | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Corporate bonds | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | International government/corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	32,407	29,115
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	32,407	29,115
Fair Value, Measurements, Recurring | International government/corporate bonds | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | International government/corporate bonds | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | International government/corporate bonds | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Diversified credit
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	103,793	94,008
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	103,793	94,008
Fair Value, Measurements, Recurring | Diversified credit | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Diversified credit | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Diversified credit | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global diversified assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	146,681	147,661
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	146,681	147,661
Fair Value, Measurements, Recurring | Global diversified assets | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global diversified assets | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global diversified assets | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global real estate investment trusts
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	53,159	57,854
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	53,159	57,854
Fair Value, Measurements, Recurring | Global real estate investment trusts | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global real estate investment trusts | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global real estate investment trusts | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global infrastructure
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	54,026	44,538
Defined Benefit Plan, Plan Assets Measured at Net Asset Value	54,026	44,538
Fair Value, Measurements, Recurring | Global infrastructure | Quoted prices in active markets of identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global infrastructure | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Fair Value, Measurements, Recurring | Global infrastructure | Significant other unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 0	$ 0