Note 13 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Recurring [Member]
Marketable equity securities	$ 1,073,706	$ 1,211,739
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable equity securities	1,073,706	1,211,739
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]
Real estate	110,503
Other investments		9,834
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Real estate	0
Other investments		0
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Real estate	0
Other investments		0
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Real estate	$ 110,503
Other investments		$ 9,834