Note 5 - Loans - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Balance at beginning of year				$ 123,279				$ 118,966	$ 123,279	$ 118,966	$ 138,963
Provision/(reversal) for loan losses		$ (1,500)		(3,000)				(2,500)	(4,500)	(2,500)	(15,650)
Charge-offs									(3,206)	(4,173)	(18,903)
Recoveries									6,818	10,986	14,556
Net Recoveries									3,612	6,813
Balance at end of year	122,391				123,279				122,391	123,279	118,966
Reserve for impaired loans	3,802				2,134				3,802	2,134
Reserve for non-impaired loans	118,589				121,145				118,589	121,145
Reserve for off-balance sheet credit commitments	2,250				4,588				2,250	4,588
Commercial Portfolio Segment [Member]
Balance at beginning of year				49,796				49,203	49,796	49,203
Provision/(reversal) for loan losses									3,936	504
Charge-offs									(629)	(3,313)
Recoveries									1,875	3,402
Net Recoveries									1,246	89
Balance at end of year	54,978				49,796				54,978	49,796	49,203
Reserve for impaired loans	1,837				43				1,837	43
Reserve for non-impaired loans	53,141				49,753				53,141	49,753
Reserve for off-balance sheet credit commitments	1,161				2,919				1,161	2,919
Real Estate Construction Portfolio Segment [Member]
Balance at beginning of year				24,838				23,268	24,838	23,268
Provision/(reversal) for loan losses									(5,389)	1,341
Charge-offs
Recoveries									177	229
Net Recoveries									177	229
Balance at end of year	19,626				24,838				19,626	24,838	23,268
Reserve for impaired loans
Reserve for non-impaired loans	19,626				24,838				19,626	24,838
Reserve for off-balance sheet credit commitments	745				1,360				745	1,360
Commercial Real Estate Portfolio Segment [Member]
Balance at beginning of year				37,610				34,864	37,610	34,864
Provision/(reversal) for loan losses									(6,289)	(3,723)
Charge-offs									(2,348)	(860)
Recoveries									4,514	7,329
Net Recoveries									2,166	6,469
Balance at end of year	33,487				37,610				33,487	37,610	34,864
Reserve for impaired loans	877				1,738				877	1,738
Reserve for non-impaired loans	32,610				35,872				32,610	35,872
Reserve for off-balance sheet credit commitments	95				114				95	114
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Balance at beginning of year				11,013				11,620	11,013	11,620
Provision/(reversal) for loan losses									3,246	(626)
Charge-offs									(229)
Recoveries									252	19
Net Recoveries									23	19
Balance at end of year	14,282				11,013				14,282	11,013	11,620
Reserve for impaired loans	1,088				353				1,088	353
Reserve for non-impaired loans	13,194				10,660				13,194	10,660
Reserve for off-balance sheet credit commitments	246				190				246	190
Installment and Other Loans [Member ]
Balance at beginning of year				$ 22				$ 11	22	11
Provision/(reversal) for loan losses									(4)	4
Charge-offs
Recoveries										7
Net Recoveries										7
Balance at end of year	18				22				18	22	$ 11
Reserve for impaired loans
Reserve for non-impaired loans	18				22				18	22
Reserve for off-balance sheet credit commitments	$ 3				$ 5				$ 3	$ 5