Note 7 - Loans (Detail) - Portfolio by Risk Rating (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Gross Loans	$ 7,364,340	$ 7,429,147
Pass [Member] | Commercial Loans Member
Gross Loans	1,870,832	1,944,989
Pass [Member] | Real Estate Construction Loans [Member]
Gross Loans	120,395	109,269
Pass [Member] | Commercial Mortgage Loans [Member]
Gross Loans	3,360,744	3,344,783
Pass [Member] | Residential Mortgage And Equity Lines Member
Gross Loans	1,358,500	1,322,768
Pass [Member] | Installment And Other Loans Member
Gross Loans	13,982	12,556
Pass [Member] | Total [Member]
Gross Loans	6,724,453	6,734,365
Special Mention [Member] | Commercial Loans Member
Gross Loans	72,872	76,776
Special Mention [Member] | Real Estate Construction Loans [Member]
Gross Loans	17,692	18,000
Special Mention [Member] | Commercial Mortgage Loans [Member]
Gross Loans	148,987	162,455
Special Mention [Member] | Residential Mortgage And Equity Lines Member
Gross Loans	1,915	816
Special Mention [Member] | Installment And Other Loans Member
Gross Loans	0	0
Special Mention [Member] | Total [Member]
Gross Loans	241,466	258,047
Substandard [Member] | Commercial Loans Member
Gross Loans	82,957	94,077
Substandard [Member] | Real Estate Construction Loans [Member]
Gross Loans	37,212	45,171
Substandard [Member] | Commercial Mortgage Loans [Member]
Gross Loans	249,608	261,214
Substandard [Member] | Residential Mortgage And Equity Lines Member
Gross Loans	14,106	16,084
Substandard [Member] | Installment And Other Loans Member
Gross Loans	0	0
Substandard [Member] | Total [Member]
Gross Loans	383,883	416,546
Doubtful [Member] | Commercial Loans Member
Gross Loans	5,128	11,265
Doubtful [Member] | Real Estate Construction Loans [Member]
Gross Loans	8,768	8,510
Doubtful [Member] | Commercial Mortgage Loans [Member]
Gross Loans	241	0
Doubtful [Member] | Residential Mortgage And Equity Lines Member
Gross Loans	401	414
Doubtful [Member] | Installment And Other Loans Member
Gross Loans	0	0
Doubtful [Member] | Total [Member]
Gross Loans	14,538	20,189
Total [Member] | Commercial Loans Member
Gross Loans	2,031,789	2,127,107
Total [Member] | Real Estate Construction Loans [Member]
Gross Loans	184,067	180,950
Total [Member] | Commercial Mortgage Loans [Member]
Gross Loans	3,759,580	3,768,452
Total [Member] | Residential Mortgage And Equity Lines Member
Gross Loans	1,374,922	1,340,082
Total [Member] | Installment And Other Loans Member
Gross Loans	13,982	12,556
Total [Member] | Total [Member]
Gross Loans	7,364,340	7,429,147
Commercial Loans Member
Gross Loans	2,031,789	2,127,107
Real Estate Construction Loans [Member]
Gross Loans	184,067	180,950
Commercial Mortgage Loans [Member]
Gross Loans	3,759,580	3,768,452
Residential Mortgage And Equity Lines Member
Gross Loans	1,374,922	1,340,082
Installment And Other Loans Member
Gross Loans	13,982	12,556
Total [Member]
Gross Loans	$ 7,364,340	$ 7,429,147