Note 5 - Loans and Allowance for Credit Losses (Details) - Recorded Investment in Loans by Impairment Method - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Recorded investment in loans:
Individually evaluated for impairment	$ 39,913	$ 45,310	$ 43,773
Collectively evaluated for impairment	4,737,052	4,267,089	3,388,775
Ending balance	4,776,965	4,312,399	3,432,548
Commercial Portfolio Segment [Member]
Recorded investment in loans:
Individually evaluated for impairment	12,869	17,612	17,785
Collectively evaluated for impairment	994,790	898,614	780,704
Ending balance	1,007,659	916,226	798,489
Income Producing Portfolio Segment [Member]
Recorded investment in loans:
Individually evaluated for impairment	6,877	5,109	2,710
Collectively evaluated for impairment	2,016,073	1,698,063	1,380,129
Ending balance	2,022,950	1,703,172	1,382,839
Owner Occupied Portfolio Segment [Member]
Recorded investment in loans:
Individually evaluated for impairment	1,790	6,891	5,054
Collectively evaluated for impairment	487,867	454,690	332,368
Ending balance	489,657	461,581	337,422
Residential Portfolio Segment [Member]
Recorded investment in loans:
Collectively evaluated for impairment	147,720	148,018	126,263
Ending balance	147,720	148,018	126,263
Construction Portfolio Segment [Member]
Recorded investment in loans:
Individually evaluated for impairment	17,644	14,241	17,479
Collectively evaluated for impairment	970,108	837,223	659,103
Ending balance	987,752	851,464	676,582
Home Equity Portfolio Segment [Member]
Recorded investment in loans:
Individually evaluated for impairment	661	1,398	745
Collectively evaluated for impairment	114,685	121,138	106,546
Ending balance	115,346	122,536	107,291
Other Consumer Portfolio Segment [Member]
Recorded investment in loans:
Individually evaluated for impairment	72	59
Collectively evaluated for impairment	5,809	109,343	3,662
Ending balance	$ 5,881	$ 109,402	$ 3,662