Fair Value of Financial Instruments (Details) - Fair Value Measurements Determined on a Nonrecurring Basis - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Fair value disclosure
Gain on investment	$ 66
Fair Value Inputs, Level 2 \| Carrying Amount
Fair value disclosure
Long-term debt, excluding finance lease and other obligations	28,210	$ 28,635
Interest rate swap contracts (see Note 11)	3	25
Fair Value Inputs, Level 2 \| Carrying Amount \| Disposal Group, Held-for-sale, Not Discontinued Operations
Fair value disclosure
Long-term debt, excluding finance lease and other obligations	1,400	1,400
Fair Value Inputs, Level 2 \| Fair Value
Fair value disclosure
Long-term debt, excluding finance lease and other obligations	27,405	29,221
Interest rate swap contracts (see Note 11)	3	25
Fair Value Inputs, Level 2 \| Fair Value \| Disposal Group, Held-for-sale, Not Discontinued Operations
Fair value disclosure
Long-term debt, excluding finance lease and other obligations	1,400	1,600
Fair Value, Inputs, Level 1 \| Fair Value
Fair value disclosure
Investment in limited partnership	$ 365	$ 299

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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