Note 6 - Stockholders' Equity (Details Textual) $ / shares in Units, $ in Thousands		3 Months Ended
	Feb. 24, 2021 $ / shares	Mar. 31, 2021 USD ($) $ / shares shares	Mar. 31, 2020 USD ($) $ / shares	Dec. 31, 2020 shares
Capital Units, Authorized (in shares)		245,000,000
Common Stock, Shares Authorized (in shares)		200,000,000		200,000,000
Preferred Stock, Shares Authorized (in shares)		20,000,000
Common Stock, Voting Rights, Votes Per Share		1
Common Stock, Dividends, Per Share, Declared (in dollars per share) | $ / shares		$ 0.08	$ 0
Dividends, Common Stock, Total | $		$ 8,000	$ 8,000
Common Stock, Capital Shares Reserved for Future Issuance (in shares)		3,260,467		4,006,948
Treasury Stock, Value, Acquired, Cost Method | $		$ 0	6,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount | $		$ 204,000
Common Class A [Member]
Common Stock, Shares Authorized (in shares)		25,000,000		25,000,000
Common Stock, Voting Rights, Votes Per Share		10
Common Stock, Dividends, Per Share, Declared (in dollars per share) | $ / shares	$ 0.08
Dividends, Common Stock, Total | $			$ 0
Common Stock, Capital Shares Reserved for Future Issuance (in shares)		1,103,015		1,336,440