Note 10 - Pension and Postretirement Benefit Plans (Details Textual) $ in Millions	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Oct. 31, 2017
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			$ (2)	$ (258)		$ (260)
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement						$ (258)
UNITED STATES | Pension Plan [Member] | Terminated Plan [Member]
Number of Plans Terminated								1
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 59
Defined Benefit Plan, Funded (Unfunded) Status of Plan, Total	$ 165			$ 165
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement							$ 256