Note 14 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Recurring [Member]
Marketable equity securities	$ 1,249,125	$ 706,954
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable equity securities	1,249,125	706,954
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable equity securities	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable equity securities		0
Fair Value, Nonrecurring [Member]
Other investments	9,834	5,464
Real estate		24,899
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Other investments	0	0
Real estate		0
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Other investments	0	0
Real estate		0
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Other investments	$ 9,834	5,464
Real estate		$ 24,899