ASSOCIATE BENEFIT PLANS - Schedule of Net Periodic Benefit Cost Components of Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Postretirement Health Coverage
Business Acquisition [Line Items]
Service cost	$ 15	$ 14	$ 30	$ 27
Interest cost	17	19	34	38
Prior service cost amortization	(19)	(19)	(38)	(38)
Net loss (gain) recognition	(9)	(16)	(18)	(31)
Net periodic cost (benefit)	4	(2)	8	(4)
Pension Plan | Alliance
Business Acquisition [Line Items]
Service cost	7	10	17	20
Interest cost	42	69	105	138
Expected return on plan assets	(79)	(148)	(196)	(295)
Prior service cost amortization	0	0	0	0
Net loss (gain) recognition	0	0	0	0
Plan settlement loss	1,431	0	1,431	0
Net periodic cost (benefit)	1,401	(69)	1,357	(137)
Pension Plan | Beneficial
Business Acquisition [Line Items]
Service cost	0	0	0	0
Interest cost	740	857	1,455	1,142
Expected return on plan assets	(1,588)	(1,442)	(3,182)	(1,923)
Prior service cost amortization	0	0	0	0
Net loss (gain) recognition	1	0	2	0
Net periodic cost (benefit)	(847)	(585)	(1,725)	(781)
Other Postretirement Benefits Plan | Beneficial
Business Acquisition [Line Items]
Service cost	29	23	58	30
Interest cost	138	177	275	236
Expected return on plan assets	0	0	0	0
Prior service cost amortization	0	0	0	0
Net loss (gain) recognition	(16)	0	(32)	0
Net periodic cost (benefit)	$ 151	$ 200	$ 301	$ 266