Note 8 - Loans - Allowance for Loan Losses by Portfolio Segment and Based on Impairment Method (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Loans individually evaluated for impairment, allowance	$ 7,525	$ 3,236
Loans individually evaluated for impairment, balance	88,129	75,859
Loans collectively evaluated for impairment, allowance	162,155	119,988
Loans collectively evaluated for impairment, balance	15,520,154	14,999,622
Loans, allowance	169,680	123,224
Loans	15,608,283	15,075,481
Commercial Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	6,895	2,543
Loans individually evaluated for impairment, balance	29,254	24,596
Loans collectively evaluated for impairment, allowance	75,361	54,478
Loans collectively evaluated for impairment, balance	2,978,712	2,754,148
Loans, allowance	82,256	57,021
Loans	3,007,966	2,778,744
Real Estate Construction Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	0	0
Loans individually evaluated for impairment, balance	4,433	4,580
Loans collectively evaluated for impairment, allowance	26,700	19,474
Loans collectively evaluated for impairment, balance	619,766	575,284
Loans, allowance	26,700	19,474
Loans	624,199	579,864
Commercial Real Estate Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	323	473
Loans individually evaluated for impairment, balance	35,629	35,070
Loans collectively evaluated for impairment, allowance	40,809	33,129
Loans collectively evaluated for impairment, balance	7,355,873	7,240,192
Loans, allowance	41,132	33,602
Loans	7,391,502	7,275,262
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	307	220
Loans individually evaluated for impairment, balance	18,813	11,613
Loans collectively evaluated for impairment, allowance	19,285	12,888
Loans collectively evaluated for impairment, balance	4,565,115	4,424,948
Loans, allowance	19,592	13,108
Loans	4,583,928	4,436,561
Installment and Other Loans [Member ]
Loans individually evaluated for impairment, allowance	0
Loans individually evaluated for impairment, balance	0
Loans collectively evaluated for impairment, allowance	0
Loans collectively evaluated for impairment, balance	688
Loans, allowance	0
Loans	688	5,050
Consumer Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance		0
Loans individually evaluated for impairment, balance		0
Loans collectively evaluated for impairment, allowance		19
Loans collectively evaluated for impairment, balance		5,050
Loans, allowance		19
Loans	$ 688	$ 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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