Note 4 - Loans and Allowance for Credit Losses (Detail) - The Company’s Recorded Investment In Loans (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Recorded investment in loans:
Individually evaluated for impairment	$ 57,918	$ 72,356	$ 47,048
Collectively evaluated for impairment	2,490,106	2,420,739	2,139,892
Ending balance	2,548,024	2,493,095	2,186,940
Commercial Loan [Member]
Recorded investment in loans:
Individually evaluated for impairment	14,395	15,177	9,395
Collectively evaluated for impairment	565,223	529,893	483,429
Ending balance	579,618	545,070	492,824
Commercial Real Estate Investment [Member]
Recorded investment in loans:
Individually evaluated for impairment	5,564	11,401	9,880
Collectively evaluated for impairment	905,265	903,237	820,104
Ending balance	910,829	914,638	829,984
Commercial Real Estate Owner Occupied [Member]
Recorded investment in loans:
Individually evaluated for impairment	6,449	8,723	2,895
Collectively evaluated for impairment	297,112	289,134	272,828
Ending balance	303,561	297,857	275,723
Residential Mortgage [Member]
Recorded investment in loans:
Collectively evaluated for impairment	69,256	61,871	43,057
Ending balance	69,256	61,871	43,057
Home Equity Line of Credit [Member]
Recorded investment in loans:
Individually evaluated for impairment	538	510	512
Collectively evaluated for impairment	108,032	106,334	94,925
Ending balance	108,570	106,844	95,437
Consumer, Other [Member]
Recorded investment in loans:
Individually evaluated for impairment		43	8
Collectively evaluated for impairment	4,117	4,242	5,149
Ending balance	4,117	4,285	5,157
Construction Loans [Member]
Recorded investment in loans:
Individually evaluated for impairment	30,972	36,502	24,358
Collectively evaluated for impairment	541,101	526,028	420,400
Ending balance	$ 572,073	$ 562,530	$ 444,758