v3.24.0.1
Note 6 - Other Income (Details Textual) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Profit (Loss) from Real Estate Operations [1],[2] $ 414 $ 381 $ 263
Land [Member] | Illinois State Toll Highway Authority [Member]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property   79  
Land [Member] | Colorado Department of Transportation [Member]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property   $ 35 $ 50
Real Estate Transaction [Member]      
Profit (Loss) from Real Estate Operations $ 107    
[1] 2023 includes a one-time $107 million transaction. 2022 includes a $79 million gain from a land sale to the Illinois State Toll Highway Authority and a $35 million gain from a sale to the Colorado Department of Transportation. 2021 includes a $50 million gain from a sale to the Colorado Department of Transportation.
[2] Prior periods have been reclassified to conform to the current period disclosure.