Note 12 - Fair Value Measurements - Financial Assets and Liabilities Measured on a Non-recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Mar. 31, 2018		Mar. 31, 2017		Dec. 31, 2017		Dec. 31, 2016
Assets, fair value disclosure	$ 1,278,667				$ 1,340,767
Total Losses	206		$ 494		874		$ 1,307
Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	46,221				73,493
Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure	148,749				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	1,129,723				1,063,054
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	5,478				5,677
Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	195				91
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	40,743				67,816
Impaired Loans [Member]
Total Losses			270		25		322
Impaired Loans [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	33,970				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	33,970				60,911
Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Total Losses			20		25		322
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	220				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	220				18,097
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Total Losses			250
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	26,131				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	26,131				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	7,619				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	7,619				11,355
Other Real Estate Owned [Member]
Total Losses	33	[1]	37	[1]	457	[2]	9	[2]
Other Real Estate Owned [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	9,821	[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]				[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	5,478	[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]			4,322	[2]
Equity Investments [Member]
Total Losses	173		$ 187		392		$ 976
Equity Investments [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	2,430				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	$ 2,430				$ 2,583

[1] Other real estate owned balance of $9.3 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.