Note 13 - Notes Payable - Senior Unsecured Notes Issuance (Details) $ in Millions	Dec. 31, 2020 USD ($)
Senior Unsecured Notes 1 [Member]
Amount Issued	$ 400
Interest Rate	1.90%
Senior Unsecured Notes 2 [Member]
Amount Issued	$ 500	[1]
Interest Rate	2.70%	[1]
Senior Unsecured Notes 3 [Member]
Amount Issued	$ 350
Interest Rate	3.70%

[1] In July 2020, the Company issued unsecured notes (the "Green Bond"), of which the net proceeds from this offering are allocated to finance or refinance, in whole or in part, recently completed, existing or future Eligible Green Projects, in alignment with the four core components of the Green Bond Principles, 2018 as administered by the International Capital Market Association. Eligible Green Projects include projects with disbursements made in the three years preceding the issue date of the notes.