Revision of Prior Period Financial Statements - Schedule of Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2024		Mar. 31, 2024	Dec. 31, 2023		Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Current Assets:
Cash and Cash Equivalents	$ 933	[1]		$ 1,353	[2]	$ 1,360	$ 956	$ 1,291	$ 1,933	[1]	$ 2,239	[1]
Materials and Supplies	414		$ 445	440	[2]	427
Other Current Assets	75		117	90	[2]	75	107	99	91
Total Current Assets	2,820		3,447	3,359	[2]	3,340	2,895	3,339	3,807
Properties	52,191		50,617	50,281	[2]	49,691	49,241	48,780	48,463
Accumulated Depreciation	(16,533)		(15,792)	(15,560)	[2]	(15,250)	(14,974)	(14,681)	(14,393)
Properties - Net (Note 6)	35,658		34,825	34,721	[2]	34,441	34,267	34,099	34,070
Other Long-term Assets	846		759	731	[2]	439	473	516	506
Total Assets	42,764		42,482	42,212	[2]	41,589	40,979	41,256	41,682
Current Liabilities:
Income and Other Taxes Payable	508		381	524	[2]	361
Labor and Fringe Benefits Payable	480			517	[2]		444	367	682
Other Current Liabilities	243			243	[2]		226	238	228
Total Current Liabilities	3,276		3,023	3,223	[2]	2,934	2,074	2,331	2,446
Deferred Income Taxes - Net (Note 12)	7,725		7,708	7,699	[2]	7,637	7,605	7,552	7,520
Total Liabilities	30,257		30,041	30,227	[2]	29,833	28,905	29,101	29,213
Shareholders' Equity:
Retained Earnings	9,988		10,011	9,609	[2]	9,513	9,852	9,935	10,229
Accumulated Other Comprehensive Loss	(232)		(273)	(279)	[2]	(394)	(412)	(408)	(410)
Total Shareholders' Equity	12,507	[3]	12,441	11,985	[2]	11,756	12,074	12,155	12,469	[3]	13,451	[3]
Total Liabilities and Shareholders' Equity	$ 42,764		42,482	42,212	[2]	41,589	40,979	41,256	41,682
As Previously Reported
Current Assets:
Cash and Cash Equivalents				1,353		1,360	956	1,291	1,958		2,239
Materials and Supplies			451	446		427
Other Current Assets			136	109		94	123	115	108
Total Current Assets			3,472	3,384		3,359	2,911	3,355	3,849
Properties			50,661	50,320		49,118	48,970	48,441	48,105
Accumulated Depreciation			(15,605)	(15,385)		(14,462)	(14,493)	(14,148)	(13,863)
Properties - Net (Note 6)			35,056	34,935		34,656	34,477	34,293	34,242
Other Long-term Assets			716	688		466	485	528	522
Total Assets			42,695	42,408		41,850	41,217	41,478	41,912
Current Liabilities:
Income and Other Taxes Payable			382	525		361
Labor and Fringe Benefits Payable							444	367	707
Other Current Liabilities							207	228	228
Total Current Liabilities			3,024	3,224		2,934	2,055	2,321	2,471
Deferred Income Taxes - Net (Note 12)			7,759	7,746		7,700	7,662	7,605	7,569
Total Liabilities			30,093	30,275		29,896	28,943	29,144	29,287
Shareholders' Equity:
Retained Earnings			10,205	9,790		9,689	10,030	10,092	10,363
Accumulated Other Comprehensive Loss			(306)	(312)		(372)	(390)	(386)	(388)
Total Shareholders' Equity			12,602	12,133		11,954	12,274	12,334	12,625		13,500
Total Liabilities and Shareholders' Equity			42,695	42,408		41,850	41,217	41,478	41,912
Adjustment
Current Assets:
Cash and Cash Equivalents				0		0	0	0	(25)		0
Materials and Supplies			(6)	(6)		0
Other Current Assets			(19)	(19)		(19)	(16)	(16)	(17)
Total Current Assets			(25)	(25)		(19)	(16)	(16)	(42)
Properties			(44)	(39)		573	271	339	358
Accumulated Depreciation			(187)	(175)		(788)	(481)	(533)	(530)
Properties - Net (Note 6)			(231)	(214)		(215)	(210)	(194)	(172)
Other Long-term Assets			43	43		(27)	(12)	(12)	(16)
Total Assets			(213)	(196)		(261)	(238)	(222)	(230)
Current Liabilities:
Income and Other Taxes Payable			(1)	(1)		0
Labor and Fringe Benefits Payable							0	0	(25)
Other Current Liabilities							19	10	0
Total Current Liabilities			(1)	(1)		0	19	10	(25)
Deferred Income Taxes - Net (Note 12)			(51)	(47)		(63)	(57)	(53)	(49)
Total Liabilities			(52)	(48)		(63)	(38)	(43)	(74)
Shareholders' Equity:
Retained Earnings			(194)	(181)		(176)	(178)	(157)	(134)
Accumulated Other Comprehensive Loss			33	33		(22)	(22)	(22)	(22)
Total Shareholders' Equity			(161)	(148)		(198)	(200)	(179)	(156)		$ (49)
Total Liabilities and Shareholders' Equity			$ (213)	$ (196)		$ (261)	$ (238)	$ (222)	$ (230)

[1] See Note 20, Revision of Prior Period Financial Statements.

[2] See Note 20, Revision of Prior Period Financial Statements.

[3] See Note 20, Revision of Prior Period Financial Statements.