Note 6 - Stockholders' Equity (Details Textual) $ / shares in Units, $ in Thousands			3 Months Ended		12 Months Ended
	Dec. 16, 2021 USD ($) $ / shares shares	Nov. 04, 2021 USD ($) $ / shares shares	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares	Nov. 05, 2019 USD ($)
Capital Units, Authorized (in shares) | shares					245,000,000
Common Stock, Shares Authorized (in shares) | shares					200,000,000	200,000,000
Preferred Stock, Shares Authorized (in shares) | shares					20,000,000
Common Stock, Voting Rights, Votes Per Share					1
Common Stock, Dividends, Per Share, Declared (in dollars per share) | $ / shares					$ 0.32	$ 0	$ 0
Dividends, Common Stock, Total | $					$ 31,000
Treasury Stock, Value, Acquired, Cost Method | $					$ 30,000	$ 75,000	$ 32,000
Common Stock, Capital Shares Reserved for Future Issuance (in shares) | shares					2,821,480	4,006,948
Repurchase Authorization 2019 [Member]
Stock Repurchase Program, Authorized Amount | $								$ 150,000
Treasury Stock, Shares, Acquired (in shares) | shares			3,688,022	1,008,091
Treasury Stock, Value, Acquired, Cost Method | $			$ 51,000	$ 21,000
Treasury Stock Acquired, Average Cost Per Share (in dollars per share) | $ / shares			$ 13.81	$ 20.83
Issuers Repurchase Program 2019 [Member]
Treasury Stock, Shares, Acquired (in shares) | shares						905,836
Treasury Stock, Value, Acquired, Cost Method | $						$ 10,000
Treasury Stock Acquired, Average Cost Per Share (in dollars per share) | $ / shares						$ 11.02
Repurchase Authorization 2020 [Member]
Treasury Stock, Shares, Acquired (in shares) | shares		864,026
Treasury Stock, Value, Acquired, Cost Method | $		$ 14,000
Treasury Stock Acquired, Average Cost Per Share (in dollars per share) | $ / shares		$ 16.47
Stock Repurchase Program, Additional Authorized Amount | $		$ 150,000
Repurchase Authorization 2021 [Member]
Treasury Stock, Shares, Acquired (in shares) | shares	1,501,088
Treasury Stock, Value, Acquired, Cost Method | $	$ 30,000
Treasury Stock Acquired, Average Cost Per Share (in dollars per share) | $ / shares	$ 19.95
Stock Repurchase Program, Remaining Authorized Repurchase Amount | $					$ 174,000
Common Class A [Member]
Common Stock, Shares Authorized (in shares) | shares					25,000,000	25,000,000
Common Stock, Voting Rights, Votes Per Share					10
Common Stock, Capital Shares Reserved for Future Issuance (in shares) | shares					847,522	1,336,440
Common Stock and Class A Common Stock [Member]
Dividends, Common Stock, Total | $						$ 0