Revision of Prior Period Financial Statements - Schedule of Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2024		Jun. 30, 2024	[3]	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	$ 1,644	[1]					$ 1,353	[2]	$ 1,360	[1]	$ 956		$ 1,291		$ 1,933	[1]	$ 2,239
Materials and Supplies	415				$ 445		440	[2]	427
Other Current Assets	93				117		90	[2]	75		107		99		91
Total Current Assets	3,577				3,447		3,359	[2]	3,340		2,895		3,339		3,807
Properties	51,503				50,617		50,281	[2]	49,691		49,241		48,780		48,463
Accumulated Depreciation	(16,333)				(15,792)		(15,560)	[2]	(15,250)		(14,974)		(14,681)		(14,393)
Properties - Net	35,170				34,825		34,721	[2]	34,441		34,267		34,099		34,070
Other Long-term Assets	795				759		731	[2]	439		473		516		506
Total Assets	43,069				42,482		42,212	[2]	41,589		40,979		41,256		41,682
Current Liabilities:
Income and Other Taxes Payable	379				381		524	[2]	361
Labor and Fringe Benefits Payable	470						517	[2]			444		367		682
Other Current Liabilities	266						243	[2]			226		238		228
Total Current Liabilities	2,569				3,023		3,223	[2]	2,934		2,074		2,331		2,446
Deferred Income Taxes - Net	7,721				7,708		7,699	[2]	7,637		7,605		7,552		7,520
Total Liabilities	30,133				30,041		30,227	[2]	29,833		28,905		29,101		29,213
Shareholders' Equity:
Retained Earnings	10,457				10,011		9,609	[2]	9,513		9,852		9,935		10,229
Accumulated Other Comprehensive Loss	(269)				(273)		(279)	[2]	(394)		(412)		(408)		(410)
Total Shareholders' Equity	12,936	[3]	$ 12,620		12,441	[3]	11,985	[2]	11,756	[4]	12,074	[4]	12,155	[4]	12,469	[4]	13,451
Total Liabilities and Shareholders' Equity	$ 43,069				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					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					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					(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					(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 11, Revision of Prior Period Financial Statements.

[2] See Note 11, Revision of Prior Period Financial Statements.

[3] See Note 11, Revision of Prior Period Financial Statements.

[4] See Note 11, Revision of Prior Period Financial Statements.