Note 3 - Accumulated Other Comprehensive Income - Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Beginning balance	$ 5,852,000	$ 7,001,000	$ 3,219,000	$ 5,174,000
Other comprehensive income (loss) before reclassifications	1,784,000	(3,035,000)	4,426,000	(1,138,000)
Amounts reclassified from accumulated other comprehensive income	(120,000)	(31,000)	(129,000)	(101,000)
Net current-period other comprehensive income (loss)	1,664,000	(3,066,000)	4,297,000	(1,239,000)
Ending balance	7,516,000	3,935,000	7,516,000	3,935,000
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Beginning balance	(428,000)	(1,535,000)	(437,000)	(299,000)
Other comprehensive income (loss) before reclassifications	0	0	0	(1,251,000)
Amounts reclassified from accumulated other comprehensive income	9,000	15,000	18,000	30,000
Net current-period other comprehensive income (loss)	9,000	15,000	18,000	(1,221,000)
Ending balance	(419,000)	(1,520,000)	(419,000)	(1,520,000)
Beginning balance	5,424,000	5,466,000	2,782,000	4,875,000
Other comprehensive income (loss) before reclassifications	1,784,000	(3,035,000)	4,426,000	(2,389,000)
Amounts reclassified from accumulated other comprehensive income	(111,000)	(16,000)	(111,000)	(71,000)
Net current-period other comprehensive income (loss)	1,673,000	(3,051,000)	4,315,000	(2,460,000)
Ending balance	$ 7,097,000	$ 2,415,000	$ 7,097,000	$ 2,415,000