General - Summary of Reclassifications to Amounts Previously Reported (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Costs and expenses:
Interest expense	$ 1,257	$ 1,316
Insurance and Other [Member]
Revenues:
Sales and service revenues	47,815	49,933
Interest, dividend and other investment income	5,632	4,338
Costs and expenses:
Cost of sales and services	38,551	40,792
Selling, general and administrative expenses	7,681	5,541
Interest expense	340	406
Railroad, Utilities and Energy [Member]
Revenues:
Utility and energy operating revenues	5,494	5,233
Service revenues and other income	878	1,032
Costs and expenses:
Utility and energy cost of sales and other expenses	4,091	4,103
Interest expense	$ 917	910
Previously Reported [Member] | Insurance and Other [Member]
Revenues:
Sales and service revenues		37,472
Interest, dividend and other investment income		4,305
Costs and expenses:
Cost of sales and services		29,395
Selling, general and administrative expenses		4,773
Interest expense		316
Previously Reported [Member] | Railroad, Utilities and Energy [Member]
Revenues:
Utility and energy operating revenues		17,690
Service revenues and other income		1,069
Costs and expenses:
Utility and energy cost of sales and other expenses		16,268
Interest expense		1,000
Reclassification [Member] | Insurance and Other [Member]
Revenues:
Sales and service revenues		12,461
Interest, dividend and other investment income		33
Costs and expenses:
Cost of sales and services		11,397
Selling, general and administrative expenses		768
Interest expense		90
Reclassification [Member] | Railroad, Utilities and Energy [Member]
Revenues:
Utility and energy operating revenues		(12,457)
Service revenues and other income		(37)
Costs and expenses:
Utility and energy cost of sales and other expenses		(12,165)
Interest expense		$ (90)