Note 16 - Fair Value of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands		Dec. 31, 2019		Dec. 31, 2018
Equity securities		$ 28,005		$ 25,098
Warrants		2,181		7,810
Equity Securities, FV-NI		28,005		25,098
Fair Value, Inputs, Level 1 [Member]
Equity securities		28,005		25,098
Equity Securities, FV-NI		28,005		25,098
Fair Value, Inputs, Level 2 [Member]
Equity securities		0		0
Equity Securities, FV-NI		0		0
Fair Value, Inputs, Level 3 [Member]
Equity securities		0		0
Equity Securities, FV-NI		0		0
Estimate of Fair Value Measurement [Member]
Cash and due from banks		177,240		225,333
Short-term investments		416,538		374,957
Securities available-for-sale		1,451,842		1,242,509
Loans, net (1)	[1]	15,444,752		13,928,162
Equity securities		28,005		25,098
Investment in Federal Home Loan Bank stock		18,090		17,250
Deposits		14,719,452		13,754,028
Short-term borrowings		25,683		0
Advances from Federal Home Loan Bank		674,530		529,500
Other borrowings		30,764		34,031
Long-term debt		76,058		132,615
Equity Securities, FV-NI		28,005		25,098
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		39		184
Warrants				184
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and due from banks		177,240		225,333
Short-term investments		416,538		374,957
Securities available-for-sale		74,936		124,751
Loans, net (1)		0	[1]	0
Equity securities		28,005		25,098
Investment in Federal Home Loan Bank stock		0		0
Deposits		0		0
Short-term borrowings		0
Advances from Federal Home Loan Bank		0		0
Other borrowings		0		0
Long-term debt		0		0
Equity Securities, FV-NI		28,005		25,098
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Warrants [Member]
Warrants		0
Warrants				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		1,376,906		1,117,758
Loans, net (1)		0	[1]	0
Equity securities		0		0
Investment in Federal Home Loan Bank stock		18,090		17,250
Deposits		0		0
Short-term borrowings		0
Advances from Federal Home Loan Bank		674,530		529,500
Other borrowings		0		0
Long-term debt		76,058		132,615
Equity Securities, FV-NI		0		0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Warrants [Member]
Warrants		0
Warrants				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)		15,444,752	[1]	13,928,162
Equity securities		0		0
Investment in Federal Home Loan Bank stock		0		0
Deposits		14,719,452		13,754,028
Short-term borrowings		25,683
Advances from Federal Home Loan Bank		0		0
Other borrowings		30,764		34,031
Long-term debt		0		0
Equity Securities, FV-NI		0		0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Warrants [Member]
Warrants		$ 39
Warrants				$ 184

[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.