Note 8 - Employee Retirement Plans - Net Periodic Benefit Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension Plan [Member]
Service cost	$ 32	$ 32
Interest cost	27	22
Expected return on plan assets	(55)	(54)
Amortization of prior service cost (credit)	1	1
Total pension and postretirement benefit expense	5	1
Other Postretirement Benefits Plan [Member]
Service cost	2	2
Interest cost	4	4
Expected return on plan assets
Amortization of prior service cost (credit)	(1)	(1)
Total pension and postretirement benefit expense	$ 5	$ 5