Fair Value of Financial Instruments - Carrying Amounts (Details) - Fair Value Measurements Determined on a Nonrecurring Basis - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Fair value disclosure
Gain (loss) on investment	$ (137)	$ (71)
Fair Value Inputs, Level 2 \| Carrying Amount
Fair value disclosure
Long-term debt, excluding finance lease and other obligations	(27,786)	(27,786)	$ (28,635)
Interest rate swap contracts (see Note 11)	0	0	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)	(1,400)
Fair Value Inputs, Level 2 \| Fair Value
Fair value disclosure
Long-term debt, excluding finance lease and other obligations	(25,041)	(25,041)	(29,221)
Interest rate swap contracts (see Note 11)	0	0	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	(1,100)	(1,100)	(1,600)
Fair Value, Inputs, Level 1 \| Fair Value
Fair value disclosure
Investment in limited partnership	$ 228	$ 228	$ 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 (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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