Note 6 - Capital Stock (Details Textual) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended		6 Months Ended
	Jul. 20, 2022	Apr. 28, 2022	Jan. 20, 2022	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Jan. 22, 2020
Stock Repurchase Program, Authorized Amount								$ 500,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 112,000		$ 112,000
Treasury Stock, Shares, Acquired (in shares)				979,000		1,362,000
Treasury Stock, Value, Acquired, Cost Method				$ 164,322	$ 81,341	$ 239,340	$ 86,580
Dividends Payable, Date Declared		Apr. 28, 2022	Jan. 20, 2022
Common Stock, Dividends, Per Share, Declared (in dollars per share)		$ 0.40	$ 0.40
Dividends Payable, Date to be Paid		May 27, 2022	Feb. 18, 2022
Dividends Payable, Date of Record		May 13, 2022	Feb. 04, 2022
Subsequent Event [Member]
Stock Repurchase Program, Authorized Amount	$ 500,000
Dividends Payable, Date Declared	Jul. 20, 2022
Common Stock, Dividends, Per Share, Declared (in dollars per share)	$ 0.40
Dividends Payable, Date to be Paid	Aug. 19, 2022
Dividends Payable, Date of Record	Aug. 05, 2022