Note 3 - Acquisitions - Pro Forma Information (Details) - Fidelity [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenues	$ 1,261,027	$ 1,186,044
Net income	$ 189,020	$ 159,348
Basic (in dollars per share)	$ 33.28	$ 28.03
Diluted (in dollars per share)	$ 32.94	$ 27.83