Note 8 - Loans - Aging of Loan Portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Loans past due	$ 113,921	$ 98,709
Non-accrual loans	52,728	48,787
Loans not past due	13,234,816	12,771,581
Loans	13,348,737	12,870,290
Financing Receivables, 30 to 59 Days Past Due [Member]
Loans past due	10,801	38,396
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due	50,392	11,526
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due
Commercial Portfolio Segment [Member]
Loans past due	63,249	30,567
Non-accrual loans	19,212	14,296
Loans not past due	2,513,400	2,430,699
Loans	2,576,649	2,461,266
Commercial Portfolio Segment [Member] \| Financing Receivables, 30 to 59 Days Past Due [Member]
Loans past due	9,537	11,079
Commercial Portfolio Segment [Member] \| Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due	34,500	5,192
Commercial Portfolio Segment [Member] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due
Real Estate Construction Portfolio Segment [Member]
Loans past due	8,040	11,213
Non-accrual loans	8,040	8,185
Loans not past due	573,877	667,592
Loans	581,917	678,805
Real Estate Construction Portfolio Segment [Member] \| Financing Receivables, 30 to 59 Days Past Due [Member]
Loans past due		3,028
Real Estate Construction Portfolio Segment [Member] \| Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due
Real Estate Construction Portfolio Segment [Member] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due
Commercial Real Estate Portfolio Segment [Member]
Loans past due	32,345	42,995
Non-accrual loans	17,154	19,820
Loans not past due	6,583,446	6,439,700
Loans	6,615,791	6,482,695
Commercial Real Estate Portfolio Segment [Member] \| Financing Receivables, 30 to 59 Days Past Due [Member]
Loans past due	841	17,573
Commercial Real Estate Portfolio Segment [Member] \| Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due	14,350	5,602
Commercial Real Estate Portfolio Segment [Member] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans past due	10,287	13,831
Non-accrual loans	8,322	6,486
Loans not past due	3,560,033	3,228,523
Loans	3,570,320	3,242,354
Residential Mortgage and Equity Lines Portfolio Segment [Member] \| Financing Receivables, 30 to 59 Days Past Due [Member]
Loans past due	423	6,613
Residential Mortgage and Equity Lines Portfolio Segment [Member] \| Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due	1,542	732
Residential Mortgage and Equity Lines Portfolio Segment [Member] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due
Installment and Other Loans [Member ]
Loans past due		103
Non-accrual loans
Loans not past due	4,060	5,067
Loans	4,060	5,170
Installment and Other Loans [Member ] \| Financing Receivables, 30 to 59 Days Past Due [Member]
Loans past due		103
Installment and Other Loans [Member ] \| Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due
Installment and Other Loans [Member ] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due

Financing receivables that are current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953401-111524

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Paragraph 2
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