Note 3 - Operations and Segmentation - Summary of Freight and Other Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue from Contract with Customer, Excluding Assessed Tax	$ 6,091	$ 5,941	$ 18,129	$ 17,960
Bulk [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	1,805	1,766	5,343	5,420
Industrial [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	2,121	2,057	6,348	6,160
Premium [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	1,842	1,722	5,331	5,190
Cargo and Freight [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	5,768	5,545	17,022	16,770
Other Subsidiary Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	179	226	608	681
Accessorial Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	122	142	427	442
Other Miscellaneous Product and Service Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 22	$ 28	$ 72	$ 67