Commitments and Contingencies - Narrative (Details) $ in Millions, $ in Millions	1 Months Ended
May 31, 2020 CAD ($) claim	Sep. 26, 2020 USD ($)
IESO Investigation of the Kapuskasing Facility
Guarantor Obligations [Line Items]
Number of investigations \| claim	2
Number of investigations finalized \| claim	4
Penalty	$ 25
Penalty due immediately	3
Penalty due over time	$ 12
Penalty payment period	10 years
Penalty deferred	$ 10
LignoTech Florida
Guarantor Obligations [Line Items]
Ownership percentage		45.00%
Borregaard ASA \| LignoTech Florida
Guarantor Obligations [Line Items]
Ownership percentage		55.00%
Financial Standby Letter of Credit
Guarantor Obligations [Line Items]
Letters of credit		$ 43
Surety Bonds
Guarantor Obligations [Line Items]
Guarantees		86
Contract Guarantee
Guarantor Obligations [Line Items]
Guarantees		$ 33

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