Note 12 - Fair Value Measurements - Financial Assets and Liabilities Measured on a Non-recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2018		Sep. 30, 2017		Dec. 31, 2017		Dec. 31, 2016
Assets, fair value disclosure	$ 1,325,569				$ 1,325,569				$ 1,340,767
Total Losses	62		$ 417		326		$ 1,044		874		$ 1,307
Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	47,587				47,587				73,493
Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure	222,896				222,896				277,622
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	1,102,505				1,102,505				1,063,054
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	4,918				4,918				5,677
Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	168				168				91
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	42,669				42,669				67,816
Impaired Loans [Member]
Total Losses							25		25		322
Impaired Loans [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	36,138				36,138				60,911
Impaired Loans [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	36,138				36,138				60,911
Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Total Losses							25		25		322
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	3,209				3,209				18,097
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	3,209				3,209				18,097
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Total Losses
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	26,606				26,606				31,459
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	26,606				26,606				31,459
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Total Losses
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	6,323				6,323				11,355
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	6,323				6,323				11,355
Other Real Estate Owned [Member]
Total Losses		[1]	405	[1]		[1]	654	[1]	457	[2]	9	[2]
Other Real Estate Owned [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	9,261	[1]			9,261	[1]			9,999	[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure		[1]				[1]				[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	4,918	[1]			4,918	[1]			5,677	[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	4,343	[1]			4,343	[1]			4,322	[2]
Equity Investments [Member]
Total Losses	62		$ 12		326		$ 365		392		$ 976
Equity Investments [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	2,188				2,188				2,583
Equity Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Equity Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Equity Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	$ 2,188				$ 2,188				$ 2,583

[1] Other real estate owned balance of $8.7 million in the condensed consolidated balance sheet is net of estimated disposal costs.

[2] Other real estate owned balance of $9.4 million in the Consolidated Balance Sheets is net of estimated disposal costs.