Note 7 - Loans - Portfolio by Risk Rating (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Loans	$ 11,365,509	$ 11,201,275
Loans held for sale	5,835	7,500
Commercial Portfolio Segment [Member]
Loans	2,152,269	2,248,187
Real Estate Construction Portfolio Segment [Member]
Loans	554,218	548,088
Commercial Real Estate Portfolio Segment [Member]
Loans	5,906,084	5,785,248
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	2,748,354	2,615,759
Consumer Portfolio Segment [Member]
Loans	4,584	3,993
Pass [Member]
Loans	10,717,240	10,513,473
Loans held for sale
Pass [Member] | Commercial Portfolio Segment [Member]
Loans	1,975,243	2,023,114
Pass [Member] | Real Estate Construction Portfolio Segment [Member]
Loans	466,878	469,909
Pass [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans	5,531,743	5,410,623
Pass [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	2,738,792	2,605,834
Pass [Member] | Consumer Portfolio Segment [Member]
Loans	4,584	3,993
Special Mention [Member]
Loans	418,609	435,032
Loans held for sale
Special Mention [Member] | Commercial Portfolio Segment [Member]
Loans	112,157	140,682
Special Mention [Member] | Real Estate Construction Portfolio Segment [Member]
Loans	45,466	44,129
Special Mention [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans	260,717	250,221
Special Mention [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	269
Special Mention [Member] | Consumer Portfolio Segment [Member]
Loans
Substandard [Member]
Loans	229,585	252,672
Loans held for sale	5,835	7,500
Substandard [Member] | Commercial Portfolio Segment [Member]
Loans	64,794	84,293
Substandard [Member] | Real Estate Construction Portfolio Segment [Member]
Loans	41,874	34,050
Substandard [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans	113,624	124,404
Substandard [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	9,293	9,925
Substandard [Member] | Consumer Portfolio Segment [Member]
Loans
Doubtful [Member]
Loans	75	98
Loans held for sale
Doubtful [Member] | Commercial Portfolio Segment [Member]
Loans	75	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