Note 4 - Loans and Allowance for Credit Losses (Detail) - Aging Analysis and the Recorded Investments in Loans Past Due (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Loans 30-59 Days Past Due	$ 18,814
Loans 60-89 Days Past Due	9,176
Loans 90 Days or More Past Due	28,166
Total Past Due Loans	56,156
Current Loans	2,491,868
Total Recorded Investment in Loans	2,548,024
Commercial Loan [Member]
Loans 30-59 Days Past Due	3,826
Loans 60-89 Days Past Due	3,358
Loans 90 Days or More Past Due	4,039
Total Past Due Loans	11,223
Current Loans	568,395
Total Recorded Investment in Loans	579,618
Commercial Real Estate Investment [Member]
Loans 30-59 Days Past Due	2,635
Loans 60-89 Days Past Due	820
Loans 90 Days or More Past Due	3,269
Total Past Due Loans	6,724
Current Loans	904,105
Total Recorded Investment in Loans	910,829
Commercial Real Estate Owner Occupied [Member]
Loans 30-59 Days Past Due	367
Loans 60-89 Days Past Due	4,081
Loans 90 Days or More Past Due	2,368
Total Past Due Loans	6,816
Current Loans	296,745
Total Recorded Investment in Loans	303,561
Real Estate Mortgage Residential [Member]
Loans 60-89 Days Past Due	107
Loans 90 Days or More Past Due	691
Total Past Due Loans	798
Current Loans	68,458
Total Recorded Investment in Loans	69,256
Home Equity Line of Credit [Member]
Loans 30-59 Days Past Due	1,344
Loans 60-89 Days Past Due	795
Loans 90 Days or More Past Due	481
Total Past Due Loans	2,620
Current Loans	105,950
Total Recorded Investment in Loans	108,570
Consumer, Other [Member]
Loans 60-89 Days Past Due	15
Total Past Due Loans	15
Current Loans	4,102
Total Recorded Investment in Loans	4,117
Construction Loans [Member]
Loans 30-59 Days Past Due	10,642
Loans 90 Days or More Past Due	17,318
Total Past Due Loans	27,960
Current Loans	544,113
Total Recorded Investment in Loans	$ 572,073