Note 2 - Cash, Cash Equivalents and Restricted Cash (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2017
Average Reserve Balances Required to be Maintained with Federal Bank	$ 110		$ 5,400
Average Excess Balances Maintained With Federal Reserve Bank		$ 199,000	258,600
Margin Deposit Assets	7,100	7,100
Restricted Cash, Total	$ 18,900	18,900	7,800
Payments for (Proceeds from) Short-term Investments, Total		(0)	(5,000)	$ (0)
Payments to Acquire Businesses, Net of Cash Acquired, Total		(0)	(0)	1,392
Net Cash Provided by (Used in) Investing Activities, Total		$ (1,381,674)	$ (1,134,327)	(903,987)
Previously Reported [Member]
Payments for (Proceeds from) Short-term Investments, Total				796,300
Payments to Acquire Businesses, Net of Cash Acquired, Total				118,400
Net Cash Provided by (Used in) Investing Activities, Total				224,700
Cash and Cash Equivalents, Period Increase (Decrease), Total				29,000
Cash and Cash Equivalents, at Carrying Value, Ending Balance				$ 247,100	$ 218,000