LONG-TERM DEBT, NET - Long-Term Debt by Types and Interest Rates (Includes Current Portion) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Other	$ 1	$ 1
Total principal long-term debt	5,500	6,144
Less: unamortized discounts	(28)	(14)
Less: unamortized debt expense	(9)	(10)
Total	5,475	6,147
Portion due within one year	150	0
Plum Creek
Debt Instrument [Line Items]
Add: fair value adjustments (related to Plum Creek merger)	12	27
9.00% debentures due 2021
Debt Instrument [Line Items]
Senior Notes	$ 150	$ 150
Debt, interest rate	9.00%	9.00%
Debt, maturity date	Dec. 31, 2021	Dec. 31, 2021
4.70% debentures due 2021
Debt Instrument [Line Items]
Senior Notes	$ 0	$ 569
Debt, interest rate	4.70%	4.70%
Debt, maturity date	Dec. 31, 2021	Dec. 31, 2021
7.125% debentures due 2023
Debt Instrument [Line Items]
Senior Notes	$ 191	$ 191
Debt, interest rate	7.125%	7.125%
Debt, maturity date	Dec. 31, 2023	Dec. 31, 2023
5.207% debentures due 2023
Debt Instrument [Line Items]
Senior Notes	$ 860	$ 860
Debt, interest rate	5.207%	5.207%
Debt, maturity date	Dec. 31, 2023	Dec. 31, 2023
4.625% notes due 2023
Debt Instrument [Line Items]
Senior Notes	$ 0	$ 500
Debt, interest rate	4.625%	4.625%
Debt, maturity date	Dec. 31, 2023	Dec. 31, 2023
3.25% debentures due 2023
Debt Instrument [Line Items]
Senior Notes	$ 0	$ 325
Debt, interest rate	3.25%	3.25%
Debt, maturity date	Dec. 31, 2023	Dec. 31, 2023
8.50% debentures due 2025
Debt Instrument [Line Items]
Senior Notes	$ 300	$ 300
Debt, interest rate	8.50%	8.50%
Debt, maturity date	Dec. 31, 2025	Dec. 31, 2025
7.95% debentures due 2025
Debt Instrument [Line Items]
Senior Notes	$ 136	$ 136
Debt, interest rate	7.95%	7.95%
Debt, maturity date	Dec. 31, 2025	Dec. 31, 2025
7.70% debentures due 2026
Debt Instrument [Line Items]
Senior Notes	$ 150	$ 150
Debt, interest rate	7.70%	7.70%
Debt, maturity date	Dec. 31, 2026	Dec. 31, 2026
7.35% debentures due 2026
Debt Instrument [Line Items]
Senior Notes	$ 62	$ 62
Debt, interest rate	7.35%	7.35%
Debt, maturity date	Dec. 31, 2026	Dec. 31, 2026
7.85% debentures due 2026
Debt Instrument [Line Items]
Senior Notes	$ 100	$ 100
Debt, interest rate	7.85%	7.85%
Debt, maturity date	Dec. 31, 2026	Dec. 31, 2026
Variable rate term loan credit facility matures 2026
Debt Instrument [Line Items]
Term loan credit facility	$ 225	$ 225
Debt, maturity date	Dec. 31, 2026	Dec. 31, 2026
6.95% debentures due 2027
Debt Instrument [Line Items]
Senior Notes	$ 300	$ 300
Debt, interest rate	6.95%	6.95%
Debt, maturity date	Dec. 31, 2027	Dec. 31, 2027
4.00% notes due 2029
Debt Instrument [Line Items]
Senior Notes	$ 750	$ 750
Debt, interest rate	4.00%	4.00%
Debt, maturity date	Dec. 31, 2029	Dec. 31, 2029
4.00% notes due 2030
Debt Instrument [Line Items]
Senior Notes	$ 750	$ 0
Debt, interest rate	4.00%	4.00%
Debt, maturity date	Dec. 31, 2030	Dec. 31, 2030
7.375% debentures due 2032
Debt Instrument [Line Items]
Senior Notes	$ 1,250	$ 1,250
Debt, interest rate	7.375%	7.375%
Debt, maturity date	Dec. 31, 2032	Dec. 31, 2032
6.875% debentures due 2033
Debt Instrument [Line Items]
Senior Notes	$ 275	$ 275
Debt, interest rate	6.875%	6.875%
Debt, maturity date	Dec. 31, 2033	Dec. 31, 2033

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Amount, after accumulated amortization, of debt discount (premium).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount of long-term debt classified as other.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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