Note 7 - Loans (Details) - Portfolio by Risk Rating - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 10,363,647	$ 10,163,452
Loans held for sale		6,676
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,851,783	9,669,161
Loans held for sale		732
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	287,256	272,066
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	213,883	210,497
Loans held for sale		5,944
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	10,725	11,728
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,251,187	2,316,863
Commercial Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,081,780	2,143,270
Commercial Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	92,891	110,338
Commercial Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	75,461	61,297
Commercial Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,055	1,958
Real Estate Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	453,469	441,543
Real Estate Construction Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	436,415	413,765
Real Estate Construction Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,197	5,776
Real Estate Construction Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	11,357	21,502
Real Estate Construction Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	500	500
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,445,575	5,301,218
Commercial Real Estate Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,131,844	5,018,199
Commercial Real Estate Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	187,237	155,553
Commercial Real Estate Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	117,324	118,196
Commercial Real Estate Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,170	9,270
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,212,072	2,101,335
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,200,400	2,091,434
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,931	399
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,741	9,502
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,344	2,493
Consumer Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 1,344	$ 2,493