Note 5 - Capital Stock (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
	Jan. 20, 2022	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Preferred Stock, Shares Outstanding, Ending Balance (in shares)		0	0	0
Common Stock, Dividends, Per Share, Declared (in dollars per share)		$ 0.30
Treasury Stock, Shares, Acquired (in shares)			879,000
Treasury Stock, Value, Acquired, Cost Method			$ 151,720	$ 92,548	$ 275,657
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 351,100	$ 351,100
Exercise or Vesting [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)		1,700,000	1,700,000
Future Issuance [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)		4,600,000	4,600,000
Subsequent Event [Member]
Dividends Payable, Date Declared	Jan. 20, 2022
Common Stock, Dividends, Per Share, Declared (in dollars per share)	$ 0.40
Dividends Payable, Date to be Paid	Feb. 18, 2022
Dividends Payable, Date of Record	Feb. 04, 2022