Note 5 - Loans (Details) - Portfolio by Risk Rating (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	$ 8,084,563	$ 7,429,147	$ 7,059,212
Commercial Loans Member | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	2,108,191	1,944,989
Commercial Loans Member | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	84,786	76,776
Commercial Loans Member | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	102,088	94,077
Commercial Loans Member | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	3,659	11,265
Commercial Loans Member | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	2,298,724	2,127,107
Commercial Loans Member
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	2,298,724	2,127,107
Real Estate Construction Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	184,449	109,269
Real Estate Construction Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans		18,000
Real Estate Construction Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	33,939	45,171
Real Estate Construction Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	3,313	8,510
Real Estate Construction Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	221,701	180,950
Real Estate Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	221,701	180,950	237,372
Commercial Mortgage Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	3,686,788	3,344,783
Commercial Mortgage Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	127,436	162,455
Commercial Mortgage Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	208,827	261,214
Commercial Mortgage Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	4,023,051	3,768,452
Commercial Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	4,023,051	3,768,452	3,748,897
Residential Mortgage And Equity Lines Member | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	1,510,647	1,322,768
Residential Mortgage And Equity Lines Member | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans		816
Residential Mortgage And Equity Lines Member | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	15,885	16,084
Residential Mortgage And Equity Lines Member | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans		414
Residential Mortgage And Equity Lines Member | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	1,526,532	1,340,082
Residential Mortgage And Equity Lines Member
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	1,526,532	1,340,082	1,186,969
Installment And Other Loans Member | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	14,555	12,556
Installment And Other Loans Member | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	14,555	12,556
Installment And Other Loans Member
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	14,555	12,556
Total [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	7,504,630	6,734,365
Total [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	212,222	258,047
Total [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	360,739	416,546
Total [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	6,972	20,189
Total [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	8,084,563	7,429,147
Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	$ 8,084,563	$ 7,429,147