Note 13 - Fair Value Measurements and Fair Value of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2022		Dec. 31, 2021		Dec. 31, 2020
Securities available-for-sale		$ 1,219,541		$ 1,127,309
Equity securities		27,740		22,319
Warrants		38,377		10,090
Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale		119,748		0
Equity securities		27,740		22,319
Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale		1,099,793		1,127,309
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		138,979		134,141		$ 134,141
Short-term investments		1,119,105		2,315,563
Securities available-for-sale		1,219,541		1,127,309		1,127,309
Loans, net		17,184,664	[1]	16,499,869	[1]	16,499,869
Equity securities		27,740		22,319		22,319
Investment in Federal Home Loan Bank stock		17,250		17,250		17,250
Deposits		18,039,184		18,051,720
Advances from Federal Home Loan Bank		20,444		21,279
Other borrowings		18,803		18,945
Long-term debt		55,126		62,274
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		24		23		$ 23
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and due from banks		138,979		134,141
Short-term investments		1,119,105		2,315,563
Securities available-for-sale		119,748		0
Loans, net	[1]	0		0
Equity securities		27,740		22,319
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		1,099,793		1,127,309
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		20,444		21,279
Other borrowings		0		0
Long-term debt		55,126		62,274
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]	17,184,664		16,499,869
Equity securities		0		0
Investment in Federal Home Loan Bank stock		0		0
Deposits		18,039,184		18,051,720
Advances from Federal Home Loan Bank		0		0
Other borrowings		18,803		18,945
Long-term debt		0		0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Warrants [Member]
Warrants		$ 24		$ 23

[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.