Note 7 - Loans (Details) - Portfolio by Risk Rating (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	$ 8,302,282	$ 8,084,563
Commercial Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	2,022,525	2,108,191
Commercial Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	111,451	84,786
Commercial Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	89,713	102,088
Commercial Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	6,191	3,659
Commercial Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	2,229,880	2,298,724
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	2,229,880	2,298,724
Real Estate Construction Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	213,529	184,449
Real Estate Construction Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	4,062
Real Estate Construction Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	32,928	33,939
Real Estate Construction Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	3,313	3,313
Real Estate Construction Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	253,832	221,701
Real Estate Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	253,832	221,701
Commercial Mortgage Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	3,858,117	3,686,788
Commercial Mortgage Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	128,977	127,436
Commercial Mortgage Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	205,893	208,827
Commercial Mortgage Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	4,192,987	4,023,051
Commercial Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	4,192,987	4,023,051
Residential Mortgage And Equity Lines Member | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	1,599,979	1,510,647
Residential Mortgage And Equity Lines Member | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	244
Residential Mortgage And Equity Lines Member | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	13,402	15,885
Residential Mortgage And Equity Lines Member | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	1,613,625	1,526,532
Residential Mortgage And Equity Lines Member
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	1,613,625	1,526,532
Installment And Other Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	11,958	14,555
Installment And Other Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	11,958	14,555
Installment And Other Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	11,958	14,555
Total [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	7,706,108	7,504,630
Total [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	244,734	212,222
Total [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	341,936	360,739
Total [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	9,504	6,972
Total [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	8,302,282	8,084,563
Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	$ 8,302,282	$ 8,084,563