Note 7 - Loans (Detail) - Allowance for Loan Losses by Portfolio Segment and Based on Impairment Method (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Loans individually evaluated for impairment
Allowance individually evaluated for impairment	$ 17,357	$ 12,183
Balance individually evaluated for impairment	230,544	248,597
Loans collectively evaluated for impairment
Allowance collectively evaluated for impairment	161,335	171,139
Balance collectively evaluated for impairment	7,133,796	7,180,550
Total allowance	178,692	183,322
Total balance	7,364,340	7,429,147
Commercial Portfolio Segment [Member]
Loans individually evaluated for impairment
Allowance individually evaluated for impairment	1,717	1,467
Balance individually evaluated for impairment	19,474	23,922
Loans collectively evaluated for impairment
Allowance collectively evaluated for impairment	59,339	64,634
Balance collectively evaluated for impairment	2,012,315	2,103,185
Total allowance	61,056	66,101
Total balance	2,031,789	2,127,107
Real Estate Construction Loans [Member]
Loans individually evaluated for impairment
Allowance individually evaluated for impairment	8,080	8,158
Balance individually evaluated for impairment	42,071	42,133
Loans collectively evaluated for impairment
Allowance collectively evaluated for impairment	12,617	14,859
Balance collectively evaluated for impairment	141,996	138,817
Total allowance	20,697	23,017
Total balance	184,067	180,950
Commercial Mortgage Loans [Member]
Loans individually evaluated for impairment
Allowance individually evaluated for impairment	6,242	1,336
Balance individually evaluated for impairment	150,750	165,885
Loans collectively evaluated for impairment
Allowance collectively evaluated for impairment	78,574	81,137
Balance collectively evaluated for impairment	3,608,830	3,602,567
Total allowance	84,816	82,473
Total balance	3,759,580	3,768,452
Residential Mortgage And Equity Lines Member
Loans individually evaluated for impairment
Allowance individually evaluated for impairment	1,318	1,222
Balance individually evaluated for impairment	18,249	16,657
Loans collectively evaluated for impairment
Allowance collectively evaluated for impairment	10,773	10,481
Balance collectively evaluated for impairment	1,356,673	1,323,425
Total allowance	12,091	11,703
Total balance	1,374,922	1,340,082
Consumer And Other Member
Loans individually evaluated for impairment
Allowance individually evaluated for impairment	0	0
Balance individually evaluated for impairment	0	0
Loans collectively evaluated for impairment
Allowance collectively evaluated for impairment	32	28
Balance collectively evaluated for impairment	13,982	12,556
Total allowance	32	28
Total balance	$ 13,982	$ 12,556