Note 8 - Income Taxes - Tax Effects of Temporary Differences and Carryforwards of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Loss and tax credit carryforwards	$ 375	$ 637
Other assets	281	269
Asset impairments and restructuring reserves	30	29
Postretirement medical and life benefits	154	171
Other accrued liabilities	354	162
Other employee benefits	329	337
Gross deferred tax assets	1,523	1,605
Valuation allowances	(138)	(167)	$ (215)	$ (317)
Total deferred tax assets	1,385	1,438
Intangible and other assets	(103)	(95)
Fixed assets	(300)	(375)
Finance leases	(174)	(160)
Total deferred tax liabilities	(577)	(630)
Net deferred tax assets	$ 808	$ 808