Note 7 - Loans - Portfolio by Risk Rating (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Loans	$ 11,571,232	$ 11,201,275
Loans held for sale		7,500
Commercial Portfolio Segment [Member]
Loans	2,215,960	2,248,187
Real Estate Construction Portfolio Segment [Member]
Loans	547,737	548,088
Commercial Real Estate Portfolio Segment [Member]
Loans	5,883,770	5,785,248
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	2,918,208	2,615,759
Consumer Portfolio Segment [Member]
Loans	5,557	3,993
Pass [Member]
Loans	10,827,950	10,513,473
Loans held for sale
Pass [Member] | Commercial Portfolio Segment [Member]
Loans	2,011,170	2,023,114
Pass [Member] | Real Estate Construction Portfolio Segment [Member]
Loans	451,043	469,909
Pass [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans	5,450,457	5,410,623
Pass [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	2,909,723	2,605,834
Pass [Member] | Consumer Portfolio Segment [Member]
Loans	5,557	3,993
Special Mention [Member]
Loans	483,100	435,032
Loans held for sale
Special Mention [Member] | Commercial Portfolio Segment [Member]
Loans	142,907	140,682
Special Mention [Member] | Real Estate Construction Portfolio Segment [Member]
Loans	51,637	44,129
Special Mention [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans	288,556	250,221
Special Mention [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans
Special Mention [Member] | Consumer Portfolio Segment [Member]
Loans
Substandard [Member]
Loans	260,129	252,672
Loans held for sale		7,500
Substandard [Member] | Commercial Portfolio Segment [Member]
Loans	61,830	84,293
Substandard [Member] | Real Estate Construction Portfolio Segment [Member]
Loans	45,057	34,050
Substandard [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans	144,757	124,404
Substandard [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	8,485	9,925
Substandard [Member] | Consumer Portfolio Segment [Member]
Loans
Doubtful [Member]
Loans	53	98
Loans held for sale
Doubtful [Member] | Commercial Portfolio Segment [Member]
Loans	53	98
Doubtful [Member] | Real Estate Construction Portfolio Segment [Member]
Loans
Doubtful [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans
Doubtful [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans
Doubtful [Member] | Consumer Portfolio Segment [Member]
Loans