Note 15 - Fair Value Measurements and Fair Value of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Securities available-for-sale		$ 1,127,309	$ 1,036,550
Equity securities		22,319	23,744
Warrants		10,090	3,409
Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale		0	80,948
Equity securities		22,319	23,744
Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale		1,127,309	955,602
Equity securities		0	0
Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale		0	0
Equity securities		0	0
Estimate of Fair Value Measurement [Member]
Cash and due from banks		134,141	138,616
Short-term investments		2,315,563	1,282,462
Securities available-for-sale		1,127,309	1,036,550
Loans, net	[1]	16,499,869	16,103,471
Equity securities		22,319	23,744
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		18,051,720	16,125,808
Advances from Federal Home Loan Bank		21,279	155,133
Other borrowings		18,945	19,632
Long-term debt		62,274	65,487
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		23	21
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and due from banks		134,141	138,616
Short-term investments		2,315,563	1,282,462
Securities available-for-sale		0	80,948
Loans, net	[1]	0	0
Equity securities		22,319	23,744
Investment in Federal Home Loan Bank stock		0	0
Deposits		0	0
Advances from Federal Home Loan Bank		0	0
Other borrowings		0	0
Long-term debt		0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Warrants [Member]
Warrants		0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and due from banks		0	0
Short-term investments		0	0
Securities available-for-sale		1,127,309	955,602
Loans, net	[1]	0	0
Equity securities		0	0
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		0	0
Advances from Federal Home Loan Bank		21,279	155,133
Other borrowings		0	0
Long-term debt		62,274	65,487
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Warrants [Member]
Warrants		0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and due from banks		0	0
Short-term investments		0	0
Securities available-for-sale		0	0
Loans, net	[1]	16,499,869	16,103,471
Equity securities		0	0
Investment in Federal Home Loan Bank stock		0	0
Deposits		18,051,720	16,125,808
Advances from Federal Home Loan Bank		0	0
Other borrowings		18,945	19,632
Long-term debt		0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Warrants [Member]
Warrants		$ 23	$ 21

[1] In accordance with the prospective adoption of ASU 2016-01, the fair value of loans as of December 31, 2019 & 2018 was measured using an exit price notion.