COMMITMENTS AND CONTINGENCIES Environmental Remediation Obligations (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2020
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 187,000,000
Accrual for environmental loss contingencies, gross	195,000,000
Liability for Asbestos and Environmental Claims, Net	112,000,000
Cass Lake, Minnesota
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	46,000,000
Kalamazoo River Superfund Site
Loss Contingencies [Line Items]
Proposed consent decree, value of remediation payments				$ 100,000,000
Proposed consent decree, value of labor performed				$ 135,700,000
Kalamazoo River Superfund Site | Time Critical Removal Action
Loss Contingencies [Line Items]
Loss contingency, damages sought, value		$ 19,000,000	$ 37,000,000
Kalamazoo River Superfund Site | Georgia-Pacific Consumer Products LP, Fort James Corporation and Georgia Pacific LLC Cost Recovery Action
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	$ 79,000,000
Responsible party percentage	15.00%
Loss Contingency, damages awarded, value	$ 50,000,000
San Jacinto River Superfund Site
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	$ 115,000,000
Responsible party percentage	50.00%
San Jacinto River Superfund Site | Northern impoundment [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	$ 105,000,000
Liability for Asbestos and Environmental Claims, Net	55,000,000
San Jacinto River Superfund Site | Southern Impoundment [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	10,000,000
Liability for Asbestos and Environmental Claims, Net	$ 10,000,000