Note 4 - Loans - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Beginning Balance				$ 122,391				$ 123,279	$ 122,391	$ 123,279	$ 118,966
Provision/(reversal) for loan losses	$ (5,000)	$ (2,000)	$ 0	0	$ 0	$ (1,500)	$ 0	(3,000)	(7,000)	(4,500)	(2,500)
Charge-offs									(6,997)	(3,206)	(4,173)
Recoveries									14,830	6,818	10,986
Net Recoveries									7,833	3,612
Ending Balance	123,224				122,391				123,224	122,391	123,279
Reserve for impaired loans	3,236				3,802				3,236	3,802
Reserve for non-impaired loans	119,988				118,589				119,988	118,589
Reserve for off-balance sheet credit commitments	3,855				2,250				3,855	2,250
Commercial Portfolio Segment [Member]
Beginning Balance				54,978				49,796	54,978	49,796
Provision/(reversal) for loan losses									4,885	3,936
Charge-offs									(6,997)	(629)
Recoveries									4,155	1,875
Net Recoveries									(2,842)	1,246
Ending Balance	57,021				54,978				57,021	54,978	49,796
Reserve for impaired loans	2,543				1,837				2,543	1,837
Reserve for non-impaired loans	54,478				53,141				54,478	53,141
Reserve for off-balance sheet credit commitments	2,301				1,161				2,301	1,161
Real Estate Construction Portfolio Segment [Member]
Beginning Balance				19,626				24,838	19,626	24,838
Provision/(reversal) for loan losses									(4,764)	(5,389)
Charge-offs									0	0
Recoveries									4,612	177
Net Recoveries									4,612	177
Ending Balance	19,474				19,626				19,474	19,626	24,838
Reserve for impaired loans	0				0				0	0
Reserve for non-impaired loans	19,474				19,626				19,474	19,626
Reserve for off-balance sheet credit commitments	1,047				745				1,047	745
Commercial Real Estate Portfolio Segment [Member]
Beginning Balance				33,487				37,610	33,487	37,610
Provision/(reversal) for loan losses									(5,216)	(6,289)
Charge-offs									0	(2,348)
Recoveries									5,331	4,514
Net Recoveries									5,331	2,166
Ending Balance	33,602				33,487				33,602	33,487	37,610
Reserve for impaired loans	473				877				473	877
Reserve for non-impaired loans	33,129				32,610				33,129	32,610
Reserve for off-balance sheet credit commitments	193				95				193	95
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Beginning Balance				14,282				11,013	14,282	11,013
Provision/(reversal) for loan losses									(1,906)	3,246
Charge-offs									0	(229)
Recoveries									732	252
Net Recoveries									732	23
Ending Balance	13,108				14,282				13,108	14,282	11,013
Reserve for impaired loans	220				1,088				220	1,088
Reserve for non-impaired loans	12,888				13,194				12,888	13,194
Reserve for off-balance sheet credit commitments	311				246				311	246
Installment and Other Loans [Member ]
Beginning Balance				$ 18				$ 22	18	22
Provision/(reversal) for loan losses									1	(4)
Charge-offs									0	0
Recoveries									0	0
Net Recoveries									0	0
Ending Balance	19				18				19	18	$ 22
Reserve for impaired loans	0				0				0	0
Reserve for non-impaired loans	19				18				19	18
Reserve for off-balance sheet credit commitments	$ 3				$ 3				$ 3	$ 3