Fair Value Measurements and Guarantees Recurring Measurements and Additional (Details) - USD ($) $ in Millions	Mar. 31, 2022		Dec. 31, 2021
Measured on a recurring basis:
Derivative Asset, Fair Value, Gross Asset	$ 861		$ 785
Derivative Liability, Fair Value, Gross Liability	(1,380)		(1,189)
Additional disclosures:
Collateral Already Posted, Aggregate Fair Value	187
Carrying Amount [Member]
Additional disclosures:
Long-term debt, including current portion	(22,426)		(23,675)
Guarantees	(39)		(39)
Fair Value [Member]
Additional disclosures:
Long-term debt, including current portion	(24,301)		(27,768)
Guarantees	(26)		(26)
Level 1 [Member]
Additional disclosures:
Long-term debt, including current portion	0		0
Guarantees	0		0
Collateral Already Posted, Aggregate Fair Value	187		296
Level 2 [Member]
Additional disclosures:
Long-term debt, including current portion	(24,301)		(27,768)
Guarantees	(10)		(10)
Level 3 [Member]
Additional disclosures:
Long-term debt, including current portion	0		0
Guarantees	(16)		(16)
Fair Value, Recurring [Member] | Carrying Amount [Member]
Measured on a recurring basis:
ARO Trust investments	250		260
Derivative Asset, Fair Value, Gross Asset	81	[1]	84	[2]
Derivative Liability, Fair Value, Gross Liability	(600)	[1]	(488)	[2]
Fair Value, Recurring [Member] | Fair Value [Member]
Measured on a recurring basis:
ARO Trust investments	250		260
Derivative Asset, Fair Value, Gross Asset	81	[1]	84	[2]
Derivative Liability, Fair Value, Gross Liability	(600)	[1]	(488)	[2]
Fair Value, Recurring [Member] | Level 1 [Member]
Measured on a recurring basis:
ARO Trust investments	250		260
Derivative Asset, Fair Value, Gross Asset	33	[1]	2	[2]
Derivative Liability, Fair Value, Gross Liability	(127)	[1]	(69)	[2]
Fair Value, Recurring [Member] | Level 2 [Member]
Measured on a recurring basis:
ARO Trust investments	0		0
Derivative Asset, Fair Value, Gross Asset	47	[1]	81	[2]
Derivative Liability, Fair Value, Gross Liability	(461)	[1]	(403)	[2]
Fair Value, Recurring [Member] | Level 3 [Member]
Measured on a recurring basis:
ARO Trust investments	0		0
Derivative Asset, Fair Value, Gross Asset	1	[1]	1	[2]
Derivative Liability, Fair Value, Gross Liability	(12)	[1]	$ (16)	[2]
WilTel Guarantee [Member]
Additional disclosures:
Guarantor Obligations, Maximum Exposure, Undiscounted	25
Indemnification Agreement [Member] | Carrying Amount [Member]
Additional disclosures:
Guarantees	$ 0

[1] Excludes approximately $187 million of net cash collateral in Level 1.

[2] Excludes approximately $296 million of net cash collateral in Level 1.