Note 6 - Gross Realized Losses on Equity and Debt Securities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Gross realized gains	$ 48	$ 562	$ 155	$ 1,365
Gross realized losses	0	(447)	(22)	(501)
Other-than-temporary impairment losses	0	0	0	0
Gross unrealized gains	375		349
Gross unrealized losses	(334)		(554)
Net gains/(losses)	89	115	(72)	864
Equity Securities [Member]
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Gross realized gains	44	131	130	856
Gross realized losses	0	0	0	0
Other-than-temporary impairment losses	0	0	0	0
Gross unrealized gains	375		349
Gross unrealized losses	(334)		(554)
Net gains/(losses)	85	131	(75)	856
Debt Securities [Member]
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Gross realized gains	4	431	25	509
Gross realized losses	0	(447)	(22)	(501)
Other-than-temporary impairment losses	0	0	0	0
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Net gains/(losses)	$ 4	$ (16)	$ 3	$ 8