Note 5 - Loans (Details) - Portfolio by Risk Rating - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 10,163,452	$ 8,914,080
Loans held for sale	6,676	973
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,669,161	8,483,654
Loans held for sale	732
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	272,066	153,589
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	210,497	274,498
Loans held for sale	5,944	973
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	11,728	2,339
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,316,863	2,382,493
Commercial Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,143,270	2,260,474
Commercial Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	110,338	47,619
Commercial Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	61,297	72,561
Commercial Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,958	1,839
Real Estate Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	441,543	298,654
Real Estate Construction Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	413,765	272,927
Real Estate Construction Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,776
Real Estate Construction Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	21,502	25,227
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	5,301,218	4,486,443
Commercial Real Estate Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,018,199	4,213,453
Commercial Real Estate Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	155,553	105,970
Commercial Real Estate Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	118,196	167,020
Commercial Real Estate Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,270
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,101,335	1,742,938
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,091,434	1,733,248
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	399
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,502	9,690
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,493	3,552
Consumer Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 2,493	$ 3,552