Note 13 - Retirement Plans and Other Postretirement Benefits (Details Textual) - USD ($) $ in Millions			12 Months Ended
	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Increase in discount rates		$ 22
Remeasurement discount rate	5.20%	5.26%	5.45%
Remeasurement of teasury rate		4.59%	4.75%
Actuarial gain (Loss)	$ (16)	$ (68)
Actuarial loss associated with asset returns	56
Partially offset by an asset actuarial gain (loss)	(8)	22
Expected rate of return on plan assets assumption			5.20%
KRIP's Projected Benefit Obligation ("PBO") [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (Loss)	(40)	(90)
Partially offset by an asset actuarial gain (loss)		$ 22
Mortality and Other Demographic Experience [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (Loss)	$ 48