Note 4 - Loans - Allowance for Loan Losses by Portfolio Segment and Based on Impairment Method (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Loans individually evaluated for impairment, allowance	$ 6,429	$ 3,236
Loans individually evaluated for impairment, balance	95,405	75,859
Loans collectively evaluated for impairment, allowance	160,109	119,988
Loans collectively evaluated for impairment, balance	15,548,991	14,999,622
Loans, allowance	166,538	123,224
Loans	15,644,396	15,075,481
Commercial Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	1,030	2,543
Loans individually evaluated for impairment, balance	27,070	24,596
Loans collectively evaluated for impairment, allowance	67,712	54,478
Loans collectively evaluated for impairment, balance	2,809,763	2,754,148
Loans, allowance	68,742	57,021
Loans	2,836,833	2,778,744
Real Estate Construction Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	0	0
Loans individually evaluated for impairment, balance	4,286	4,580
Loans collectively evaluated for impairment, allowance	30,854	19,474
Loans collectively evaluated for impairment, balance	675,206	575,284
Loans, allowance	30,854	19,474
Loans	679,492	579,864
Commercial Real Estate Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	5,254	473
Loans individually evaluated for impairment, balance	53,289	35,070
Loans collectively evaluated for impairment, allowance	43,951	33,129
Loans collectively evaluated for impairment, balance	7,501,738	7,240,192
Loans, allowance	49,205	33,602
Loans	7,555,027	7,275,262
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	145	220
Loans individually evaluated for impairment, balance	10,760	11,613
Loans collectively evaluated for impairment, allowance	17,592	12,888
Loans collectively evaluated for impairment, balance	4,559,184	4,424,948
Loans, allowance	17,737	13,108
Loans	4,569,944	4,436,561
Installment and Other Loans [Member ]
Loans individually evaluated for impairment, allowance	0	0
Loans individually evaluated for impairment, balance	0	0
Loans collectively evaluated for impairment, allowance	0	19
Loans collectively evaluated for impairment, balance	3,100	5,050
Loans, allowance	0	19
Loans	$ 3,100	$ 5,050

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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