Note 7 - Loans (Details) - Portfolio by Risk Rating (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	$ 7,832,013	$ 7,429,147
Commercial Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	2,047,158	1,944,989
Commercial Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	84,776	76,776
Commercial Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	94,088	94,077
Commercial Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	11,880	11,265
Commercial Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	2,237,902	2,127,107
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	2,237,902	2,127,107
Real Estate Construction Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	151,696	109,269
Real Estate Construction Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	0	18,000
Real Estate Construction Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	34,676	45,171
Real Estate Construction Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	3,495	8,510
Real Estate Construction Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	189,867	180,950
Real Estate Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	189,867	180,950
Commercial Mortgage Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	3,543,731	3,344,783
Commercial Mortgage Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	137,183	162,455
Commercial Mortgage Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	240,434	261,214
Commercial Mortgage Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	0	0
Commercial Mortgage Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	3,921,348	3,768,452
Commercial Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	3,921,348	3,768,452
Residential Mortgage And Equity Lines Member | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	1,453,498	1,322,768
Residential Mortgage And Equity Lines Member | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	0	816
Residential Mortgage And Equity Lines Member | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	14,149	16,084
Residential Mortgage And Equity Lines Member | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	0	414
Residential Mortgage And Equity Lines Member | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	1,467,647	1,340,082
Residential Mortgage And Equity Lines Member
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	1,467,647	1,340,082
Installment And Other Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	15,249	12,556
Installment And Other Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	0	0
Installment And Other Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	0	0
Installment And Other Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	0	0
Installment And Other Loans [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	15,249	12,556
Installment And Other Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	15,249	12,556
Total [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	7,211,332	6,734,365
Total [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	221,959	258,047
Total [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	383,347	416,546
Total [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	15,375	20,189
Total [Member] | Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	7,832,013	7,429,147
Total [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross Loans	$ 7,832,013	$ 7,429,147