Note 2 - Sales/Mergers/Acquisitions - Acquisition of the Bates Companies (Details) - USD ($)		12 Months Ended
	Oct. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Feb. 12, 2019	Dec. 31, 2017
Business Acquisition [Line Items]
Cash paid			$ 9,834,000
Common stock consideration			81,637,000
Interest rate (as a percent)					5.375%
Business acquisition related costs			1,795,000
Intangibles			10,064,000
Goodwill		$ 74,748,000	77,832,000	$ 74,066,000		$ 28,334,000
Bates Companies
Business Acquisition [Line Items]
Assets under management	$ 704,000,000
Voting interests acquired (as a percent)	100.00%
Cash paid	$ 3,000,000.0		$ 1,400,000
Cash consideration paid from operating cash	$ 1,500,000
Stock issued during period (in shares)			23,501
Stock consideration			$ 3,000,000.0
Number of shares expecting to issue based on 10-day volume weighted average of the closing stock price of the Company ending five days prior to closing			47,003
Business acquisition related costs			$ 394,000
Goodwill				3,700,000
Other Liabilities. | Bates Companies
Business Acquisition [Line Items]
Business combination, contingent consideration			$ 2,000,000.0
Customer Lists [Member] | Bates Companies
Business Acquisition [Line Items]
Intangibles				$ 1,600,000
Promissory Note [Member] | Bates Companies
Business Acquisition [Line Items]
Repayment period (in years)	5 years
Frequency of installments	annual installments
Periodic payment of principal amount	$ 300,000
Interest rate (as a percent)	2.18%
Promissory Note [Member] | Other Liabilities. | Bates Companies
Business Acquisition [Line Items]
Promissory note	$ 1,500,000
Maximum | Bates Companies
Business Acquisition [Line Items]
Common stock consideration	$ 3,000,000.0
Common Stock [Member] | Bates Companies
Business Acquisition [Line Items]
Stock issued during period (in shares)		9,400