Note 20 - Revenue from Contracts with Customers - Revenue by Operating Segment (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017		Jun. 30, 2018		Jun. 30, 2017
Total non-interest income		$ 11,435		$ 11,525		$ 22,344		$ 22,147
Commercial Banking [Member]
Total non-interest income		6,091		6,372		11,500		11,900
Investment Management and Trust [Member]
Total non-interest income		5,344		5,153		10,844		10,247
Fiduciary and Trust [Member]
Non-interest income		5,344		5,153		10,844		10,247
Fiduciary and Trust [Member] | Commercial Banking [Member]
Non-interest income
Fiduciary and Trust [Member] | Investment Management and Trust [Member]
Non-interest income		5,344		5,153		10,844		10,247
Deposit Account [Member]
Non-interest income		1,447		1,516		2,858		3,015
Deposit Account [Member] | Commercial Banking [Member]
Non-interest income		1,447		1,516		2,858		3,015
Deposit Account [Member] | Investment Management and Trust [Member]
Non-interest income
Credit and Debit Card [Member]
Non-interest income		1,689		1,514		3,197		2,920
Credit and Debit Card [Member] | Commercial Banking [Member]
Non-interest income		1,689		1,514		3,197		2,920
Credit and Debit Card [Member] | Investment Management and Trust [Member]
Non-interest income
Treasury Management [Member]
Non-interest income		1,113		1,082		2,160		2,104
Treasury Management [Member] | Commercial Banking [Member]
Non-interest income		1,113		1,082		2,160		2,104
Treasury Management [Member] | Investment Management and Trust [Member]
Non-interest income
Mortgage Banking [Member]
Non-interest income	[1]	746		897		1,322		1,599
Mortgage Banking [Member] | Commercial Banking [Member]
Non-interest income	[1]	746		897		1,322		1,599
Mortgage Banking [Member] | Investment Management and Trust [Member]
Non-interest income	[1]
Investment Advisory, Management and Administrative Service [Member]
Non-interest income		397		357		801		743
Investment Advisory, Management and Administrative Service [Member] | Commercial Banking [Member]
Non-interest income		397		357		801		743
Investment Advisory, Management and Administrative Service [Member] | Investment Management and Trust [Member]
Non-interest income
Life Insurance Product Line [Member]
Non-interest income	[1]	191		556		378		760
Life Insurance Product Line [Member] | Commercial Banking [Member]
Non-interest income	[1]	191		556		378		760
Life Insurance Product Line [Member] | Investment Management and Trust [Member]
Non-interest income	[1]
Product and Service, Other [Member]
Non-interest income		508	[2]	450	[3]	784	[2]	759	[3]
Product and Service, Other [Member] | Commercial Banking [Member]
Non-interest income		508	[2]	450	[3]	784	[2]	759	[3]
Product and Service, Other [Member] | Investment Management and Trust [Member]
Non-interest income			[2]		[3]		[2]		[3]

[1] Not within the scope of ASC 606

[2] includes safe box deposit fees of $46,000 quarterly and $91,000 year-to-date included within the scope of ASC 606

[3] includes safe box deposit fees of $40,000 quarterly and $85,000 year-to-date included within the scope of ASC 606