PENSION AND OTHER POSTRETIREMENT BENEFITS - Schedule of Defined Benefit Plans Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1,387	$ 1,875	$ 4,187	$ 4,691
Interest Cost	4,307	3,818	12,971	9,642
Expected Return on Plan Assets	(5,077)	(5,256)	(15,213)	(12,908)
Amortizations:
Prior Service Cost	26	26	79	84
Actuarial Loss	2,398	2,878	7,195	8,642
Net Periodic Benefit Cost	3,041	3,341	9,219	10,151
Capitalized Benefit Cost	(454)	(762)	(1,423)	(1,799)
Deferred Benefit Cost	(516)	(594)	(1,710)	(1,719)
Total Net Periodic Benefit Expense	2,071	1,985	6,086	6,633
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	129	251	400	692
Interest Cost	729	644	2,163	1,720
Expected Return on Plan Assets	(1,147)	(1,129)	(3,428)	(3,012)
Amortizations:
Prior Service Cost	(144)	(74)	(432)	(246)
Actuarial Loss	292	223	876	674
Net Periodic Benefit Cost	(141)	(85)	(421)	(172)
Capitalized Benefit Cost	(115)	263	(270)	258
Deferred Benefit Cost	118	0	352	0
Total Net Periodic Benefit Expense	$ (138)	$ 178	$ (339)	$ 86