Note 4 - Revenue Recognition From Contracts With Customers - Sources of Non-interest Income (Details) - USD ($)		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
Noninterest income										$ 43,626,000		$ 32,434,000
Net Gains on Sale of Loans										171,000	[1]	458,000
Net gains on sales of investments											[1]	199,000
Net Change in Fair Value of Equity Securities										(63,000)	[1]
Net Gains on Purchased Tax Credits										44,000	[1]	57,000
Net Loss on Disposal of Fixed Assets										(137,000)	[1]
Income from Bank-Owned Life Insurance										509,000	[1]	464,000
Other										135,000	[1]	105,000
Noninterest Income		$ 2,040,000	$ 2,088,000	$ 2,125,000	$ 2,086,000	$ 1,940,000	$ 1,818,000	$ 1,966,000	$ 2,076,000	8,339,000		7,800,000
Noninterest Expense		$ 9,375,000	$ 9,365,000	$ 9,494,000	$ 6,667,000	$ 6,754,000	$ 5,897,000	$ 6,304,000	$ 6,217,000	34,901,000		25,172,000
Net non-interest income										8,291,000
Accounting Standards Update 2014-09 [Member]
Other										135,000
Noninterest Income										7,815,000
Other Real Estate Owned Expense										48,000
Noninterest Expense										48,000
Deposit Account [Member]
Noninterest income										2,970,000		2,482,000
Deposit Account [Member] | Accounting Standards Update 2014-09 [Member]
Noninterest income	[2]									2,970,000
Insurance Commissions [Member]
Noninterest income										3,763,000		3,583,000
Insurance Commissions [Member] | Accounting Standards Update 2014-09 [Member]
Noninterest income										3,763,000
Financial Service, Other [Member]
Noninterest income										947,000		$ 452,000
Financial Service, Other [Member] | Accounting Standards Update 2014-09 [Member]
Noninterest income	[3]									$ 947,000

[1] Not within the scope of ASC 606.

[2] Interchange fees and ATM fees are included within this line item.

[3] The Other Commissions category includes wealth management referral fees, merchant services fees, check sales and safety deposit box rentals totaling $460,000 for the year ended December 31, 2018, which is in the scope of ASC 606; the remaining balance of $487,000 for the year ended December 31, 2018, mainly represents income derived from an assumable rate conversion ("ARC") loan referral fee and a bank-owned life insurance policy claim for the year ended December 31, 2018, which are outside the scope of ASC 606. The following narrative describes the Company's revenue streams accounted for under the guidance of ASC 606 as follows: