Pension and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Cost Relating to Pension and OPEB Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Non-operating credits	$ (11)	$ 0	$ (47)
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations | Paper mill at Thorold (Ontario)
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Curtailments, settlements and other (gains) losses		28
Pension Plans
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Interest cost	133	151	181
Expected return on plan assets	(215)	(226)	(251)
Amortization of prior service costs or credits	1	0	0
Amortization of actuarial losses (gains)	78	63	34
Non-operating credits	(3)	(12)	(36)
Service cost	16	14	15
Net periodic benefit costs (credits) before special events	13	2	(21)
Curtailments, settlements and other (gains) losses	(1)	32	0
Net periodic benefit cost	12	34	(21)
OPEB Plans
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Interest cost	3	4	6
Expected return on plan assets	0	0	0
Amortization of prior service costs or credits	(4)	(4)	(11)
Amortization of actuarial losses (gains)	(6)	(6)	(6)
Non-operating credits	(7)	(6)	(11)
Service cost	1	1	0
Net periodic benefit costs (credits) before special events	(6)	(5)	(11)
Curtailments, settlements and other (gains) losses	0	(14)	0
Net periodic benefit cost	$ (6)	$ (19)	$ (11)