Note 20 - Revenue from Contracts with Customers - Revenue by Operating Segment (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Total non-interest income		$ 10,923	$ 10,644
Commercial Banking [Member]
Total non-interest income		5,423	5,550
Investment Management and Trust [Member]
Total non-interest income		5,500	5,094
Fiduciary and Trust [Member]
Non-interest income		5,500	5,094
Fiduciary and Trust [Member] | Commercial Banking [Member]
Non-interest income
Fiduciary and Trust [Member] | Investment Management and Trust [Member]
Non-interest income		5,500	5,094
Deposit Account [Member]
Non-interest income		1,511	1,565
Deposit Account [Member] | Commercial Banking [Member]
Non-interest income		1,511	1,565
Deposit Account [Member] | Investment Management and Trust [Member]
Non-interest income
Credit and Debit Card [Member]
Non-interest income		1,508	1,406
Credit and Debit Card [Member] | Commercial Banking [Member]
Non-interest income		1,508	1,406
Credit and Debit Card [Member] | Investment Management and Trust [Member]
Non-interest income
Treasury Management [Member]
Non-interest income		947	956
Treasury Management [Member] | Commercial Banking [Member]
Non-interest income		947	956
Treasury Management [Member] | Investment Management and Trust [Member]
Non-interest income
Mortgage Banking [Member]
Non-interest income	[1]	576	702
Mortgage Banking [Member] | Commercial Banking [Member]
Non-interest income	[1]	576	702
Mortgage Banking [Member] | Investment Management and Trust [Member]
Non-interest income	[1]
Investment Advisory, Management and Administrative Service [Member]
Non-interest income		404	386
Investment Advisory, Management and Administrative Service [Member] | Commercial Banking [Member]
Non-interest income		404	386
Investment Advisory, Management and Administrative Service [Member] | Investment Management and Trust [Member]
Non-interest income
Life Insurance Product Line [Member]
Non-interest income	[1]	187	204
Life Insurance Product Line [Member] | Commercial Banking [Member]
Non-interest income	[1]	187	204
Life Insurance Product Line [Member] | Investment Management and Trust [Member]
Non-interest income	[1]
Product and Service, Other [Member]
Non-interest income	[2]	290	331
Product and Service, Other [Member] | Commercial Banking [Member]
Non-interest income	[2]	290	331
Product and Service, Other [Member] | Investment Management and Trust [Member]
Non-interest income	[2]

[1] Not within the scope of ASC 606

[2] includes safety box deposit fees of $45 thousand included within the scope of ASC 606